[DOXIA-688] Remove empty alt attribute value on images which causes the browser not to render replacement icon

See: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#attr-alt
diff --git a/doxia-core/src/main/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSink.java b/doxia-core/src/main/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSink.java
index cecca4d..eb04738 100644
--- a/doxia-core/src/main/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSink.java
+++ b/doxia-core/src/main/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSink.java
@@ -923,10 +923,6 @@
         atts.addAttribute(Attribute.SRC, HtmlTools.escapeHTML(src, true));
         atts.addAttributes(filtered);
 
-        if (atts.getAttribute(Attribute.ALT.toString()) == null) {
-            atts.addAttribute(Attribute.ALT.toString(), "");
-        }
-
         writeStartTag(HtmlMarkup.IMG, atts, true);
     }
 
diff --git a/doxia-core/src/test/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSinkTest.java b/doxia-core/src/test/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSinkTest.java
index e85317c..221338d 100644
--- a/doxia-core/src/test/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSinkTest.java
+++ b/doxia-core/src/test/java/org/apache/maven/doxia/sink/impl/Xhtml5BaseSinkTest.java
@@ -645,7 +645,7 @@
         }
 
         assertEquals(
-                "<figure style=\"bold\">" + "<img src=\"src.jpg\" style=\"bold\" alt=\"\" />"
+                "<figure style=\"bold\">" + "<img src=\"src.jpg\" style=\"bold\" />"
                         + "<figcaption style=\"bold\"></figcaption></figure>",
                 writer.toString());
     }
@@ -664,7 +664,7 @@
             sink.close();
         }
 
-        assertEquals("<img src=\"source.png\" style=\"bold\" alt=\"\" />", writer.toString());
+        assertEquals("<img src=\"source.png\" style=\"bold\" />", writer.toString());
     }
 
     /**
diff --git a/doxia-modules/doxia-module-xdoc/src/test/java/org/apache/maven/doxia/module/xdoc/XdocSinkTest.java b/doxia-modules/doxia-module-xdoc/src/test/java/org/apache/maven/doxia/module/xdoc/XdocSinkTest.java
index f804921..227c652 100644
--- a/doxia-modules/doxia-module-xdoc/src/test/java/org/apache/maven/doxia/module/xdoc/XdocSinkTest.java
+++ b/doxia-modules/doxia-module-xdoc/src/test/java/org/apache/maven/doxia/module/xdoc/XdocSinkTest.java
@@ -213,7 +213,7 @@
 
     /** {@inheritDoc} */
     protected String getFigureBlock(String source, String caption) {
-        String figureBlock = "<figure><img src=\"" + escapeHTML(source) + "\"  alt=\"\" />";
+        String figureBlock = "<figure><img src=\"" + escapeHTML(source) + "\" />";
         if (caption != null) {
             figureBlock += "<figcaption>" + caption + "</figcaption>";
         }
diff --git a/doxia-modules/doxia-module-xhtml5/src/test/java/org/apache/maven/doxia/module/xhtml5/Xhtml5SinkTest.java b/doxia-modules/doxia-module-xhtml5/src/test/java/org/apache/maven/doxia/module/xhtml5/Xhtml5SinkTest.java
index 71724a8..82df0d9 100644
--- a/doxia-modules/doxia-module-xhtml5/src/test/java/org/apache/maven/doxia/module/xhtml5/Xhtml5SinkTest.java
+++ b/doxia-modules/doxia-module-xhtml5/src/test/java/org/apache/maven/doxia/module/xhtml5/Xhtml5SinkTest.java
@@ -200,7 +200,7 @@
 
     /** {@inheritDoc} */
     protected String getFigureBlock(String source, String caption) {
-        String figureBlock = "<figure><img src=\"" + escapeHTML(source, true) + "\" alt=\"\" />";
+        String figureBlock = "<figure><img src=\"" + escapeHTML(source, true) + "\" />";
         if (caption != null) {
             figureBlock += "<figcaption>" + caption + "</figcaption>";
         }
diff --git a/doxia-modules/doxia-module-xhtml5/src/test/resources/index.xml.vm b/doxia-modules/doxia-module-xhtml5/src/test/resources/index.xml.vm
index 4c56c01..1cee8e2 100644
--- a/doxia-modules/doxia-module-xhtml5/src/test/resources/index.xml.vm
+++ b/doxia-modules/doxia-module-xhtml5/src/test/resources/index.xml.vm
@@ -43,7 +43,7 @@
       <span style="display: block; text-align: right; font-size: smaller">Released: 20 June 2007</span>
       <p>
         <a href="download.html">
-          <img src="images/folder-open.gif" border="0" alt="" title="Download Maven ${currentVersion}"/>
+          <img src="images/folder-open.gif" title="Download Maven ${currentVersion}"/>
           Maven ${currentVersion}
         </a>
         <small>(1.3Mb)</small>
@@ -56,7 +56,7 @@
       </p>
       <p>
         <a href="download.html">
-          <img src="images/folder-open.gif" border="0" alt="" title="Download Maven Tasks for Ant 2.0.7"/>
+          <img src="images/folder-open.gif" title="Download Maven Tasks for Ant 2.0.7"/>
           Maven Tasks for Ant 2.0.7
         </a>
         <small>(938k)</small>
@@ -71,7 +71,7 @@
       <h4>Other Maven Projects</h4>
       <p>
         <a href="/continuum/">
-          <img src="images/continuum.png" border="0" width="76" height="32" style="float: left; margin-right: 1em;" alt="" title="Continuum" />
+          <img src="images/continuum.png" width="76" height="32" style="float: left; margin-right: 1em;" title="Continuum" />
         Continuum
         </a>
         continuous integration server
@@ -83,7 +83,7 @@
 
       <p>
         <a href="archiva">
-          <img src="images/archiva.png" border="0" width="76" height="32" style="float: left; margin-right: 1em;" alt="" title="Archiva" />
+          <img src="images/archiva.png" width="76" height="32" style="float: left; margin-right: 1em;" title="Archiva" />
         Archiva
         </a>
         repository and artifact management server
@@ -91,7 +91,7 @@
       -->
       <p>
         <a href="/maven-1.x/">
-          <img src="images/maven-1.x.png" border="0" width="76" height="32" style="float: left; margin-right: 1em;" alt="" title="Maven 1.x" />
+          <img src="images/maven-1.x.png" width="76" height="32" style="float: left; margin-right: 1em;" title="Maven 1.x" />
         Maven 1.x
         </a>
         All stories start at the beginning...
diff --git a/doxia-test-docs/src/main/resources/maven-site/xdoc/index.xml.vm b/doxia-test-docs/src/main/resources/maven-site/xdoc/index.xml.vm
index 985b437..b023079 100644
--- a/doxia-test-docs/src/main/resources/maven-site/xdoc/index.xml.vm
+++ b/doxia-test-docs/src/main/resources/maven-site/xdoc/index.xml.vm
@@ -43,7 +43,7 @@
       <span style="display: block; text-align: right; font-size: smaller">Released: 10 April 2008</span>
       <p>
         <a href="download.html">
-          <img src="images/folder-open.gif" border="0" alt="" title="Download Maven ${currentVersion}"/>
+          <img src="images/folder-open.gif" title="Download Maven ${currentVersion}"/>
           Maven ${currentVersion}
         </a>
         <small>(1.6Mb)</small>
@@ -56,7 +56,7 @@
       </p>
       <p>
         <a href="download.html">
-          <img src="images/folder-open.gif" border="0" alt="" title="Download Maven Tasks for Ant 2.0.9"/>
+          <img src="images/folder-open.gif" title="Download Maven Tasks for Ant 2.0.9"/>
           Maven Tasks for Ant 2.0.9
         </a>
         <small>(994k)</small>