Clean up shutdown process

src/qt/bitcoin.cpp

@@ -260,9 +260,9 @@ int main(int argc, char *argv[])
                 guiref = 0;
             }
             // Shutdown the core and its threads, but don't exit Bitcoin-Qt here
-            Shutdown(NULL);
             threadGroup.interrupt_all();
             threadGroup.join_all();
+            Shutdown();
         }
         else
         {