SLING-9783 - The HTL compiler will trigger a NPE if a null value should be written into an HTML attribute

* checked if the passed values in the context of attributes are not null
* performed some Yoda comparisons in cases where attribute values could be null
* updated the io.sightly.tck which provides additional tests for attributes to which
null values can be passed
diff --git a/pom.xml b/pom.xml
index 2ec8638..f1f2d75 100644
--- a/pom.xml
+++ b/pom.xml
@@ -179,7 +179,7 @@
         <dependency>
             <groupId>io.sightly</groupId>
             <artifactId>io.sightly.tck</artifactId>
-            <version>1.4.2</version>
+            <version>1.4.3</version>
         </dependency>
         <dependency>
             <groupId>org.osgi</groupId>