Bug 785744 - Async file picker cleanup. r=neil

widget/xpwidgets/nsBaseFilePicker.cpp

@@ -51,15 +51,16 @@ public:
     // It's possible that some widget implementations require GUI operations
     // to be on the main thread, so that's why we're not dispatching to another
     // thread and calling back to the main after it's done.
-    int16_t result;
+    int16_t result = nsIFilePicker::returnCancel;
     nsresult rv = mFilePicker->Show(&result);
     if (NS_FAILED(rv)) {
       NS_ERROR("FilePicker's Show() implementation failed!");
-      mCallback->Done(nsIFilePicker::returnCancel);
-      return NS_OK;
     }
 
-    return mCallback->Done(result);
+    if (mCallback) {
+      mCallback->Done(result);
+    }
+    return NS_OK;
   }
 
 private: