Bug 801723. WebIDL binding objects may not have classinfo even if they're nsISupports. r=peterv

js/xpconnect/src/XPCJSID.cpp

@@ -484,6 +484,10 @@ nsJSIID::HasInstance(nsIXPConnectWrappedNative *wrapper,
         nsISupports *identity;
         if (mozilla::dom::UnwrapDOMObjectToISupports(obj, identity)) {
             nsCOMPtr<nsIClassInfo> ci = do_QueryInterface(identity);
+            if (!ci) {
+                // No classinfo means we're not implementing interfaces and all
+                return NS_OK;
+            }
 
             XPCCallContext ccx(JS_CALLER, cx);