FOP-2317: crash when issuing warning for invalid property value

Patch by Seifeddine Dridi


git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1544199 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/fo/FObj.java

@@ -149,7 +149,7 @@ public abstract class FObj extends FONode implements Constants {
             String attributeName = attList.getQName(i);
             String attributeValue = attList.getValue(i);
             Property prop = propertyList.getPropertyForAttribute(attList, attributeName, attributeValue);
-            if (prop.equals(value)) {
+            if (prop != null && prop.equals(value)) {
                 return attributeName;
             }
         }