Make sure that an A entry in an annotation dictionary is also a dicti…

…onary itself

src/core/annotation.js

@@ -485,7 +485,7 @@ var LinkAnnotation = (function LinkAnnotationClosure() {
     data.annotationType = AnnotationType.LINK;
 
     var action = dict.get('A');
-    if (action) {
+    if (action && isDict(action)) {
       var linkType = action.get('S').name;
       if (linkType === 'URI') {
         var url = action.get('URI');