SLING-11362 Prevent potential ClassCastException in tearDown (#13)

diff --git a/core/src/main/java/org/apache/sling/testing/mock/sling/context/SlingContextImpl.java b/core/src/main/java/org/apache/sling/testing/mock/sling/context/SlingContextImpl.java
index a8b0b48..029d84a 100644
--- a/core/src/main/java/org/apache/sling/testing/mock/sling/context/SlingContextImpl.java
+++ b/core/src/main/java/org/apache/sling/testing/mock/sling/context/SlingContextImpl.java
@@ -217,9 +217,9 @@
     protected void tearDown() {
 
         if (this.request != null) {
-            MockSlingBindings slingBindings = (MockSlingBindings)this.request.getAttribute(SlingBindings.class.getName());
-            if (slingBindings != null) {
-                slingBindings.tearDown();
+            SlingBindings slingBindings = (SlingBindings)this.request.getAttribute(SlingBindings.class.getName());
+            if (slingBindings instanceof MockSlingBindings) {
+                ((MockSlingBindings)slingBindings).tearDown();
             }
         }
 
diff --git a/core/src/test/java/org/apache/sling/testing/mock/sling/context/AbstractSlingContextImplTest.java b/core/src/test/java/org/apache/sling/testing/mock/sling/context/AbstractSlingContextImplTest.java
index a40c75f..65e0b43 100644
--- a/core/src/test/java/org/apache/sling/testing/mock/sling/context/AbstractSlingContextImplTest.java
+++ b/core/src/test/java/org/apache/sling/testing/mock/sling/context/AbstractSlingContextImplTest.java
@@ -83,6 +83,14 @@
     }
 
     @Test
+    public void testNonMockedSlingBindings() {
+        final SlingBindings slingBindings = new SlingBindings();
+        context.request().setAttribute(SlingBindings.class.getName(), slingBindings);
+        SlingBindings bindings = (SlingBindings) context.request().getAttribute(SlingBindings.class.getName());
+        assertNotNull(bindings);
+    }
+
+    @Test
     public void testSetCurrentResource() {
         context.currentResource("/content/sample/en/jcr:content/par/colctrl");
         assertEquals("/content/sample/en/jcr:content/par/colctrl", context.currentResource().getPath());