Guard an unsafe cast of a catch context's extension object.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 4b8a8aa98887da423cbb6e4c3f287ea077504ec4..6185e2dcf049484646a37600c1f944222e18b4b9 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3228,8 +3228,8 @@ bool JSObject::ReferencesObject(Object* obj) {
       }
     }
 
-    // Check the context extension if any.
-    if (context->has_extension()) {
+    // Check the context extension (if any) if it can have references.
+    if (context->has_extension() && !context->IsCatchContext()) {
       return JSObject::cast(context->extension())->ReferencesObject(obj);
     }
   }