Null-check to fix crash. b=601543 r+a=jonas

content/xslt/src/xslt/txMozillaXSLTProcessor.cpp

@@ -919,7 +919,7 @@ txMozillaXSLTProcessor::SetParameter(const nsAString & aNamespaceURI,
 
                 if (NS_FAILED(rv)) {
                     while (i < count) {
-                        NS_RELEASE(values[i]);
+                        NS_IF_RELEASE(values[i]);
                         ++i;
                     }
                     nsMemory::Free(array);