debugger: clean register view after debugging finished

(cherry picked from commit cce7bf9fa2)

src/plugins/debugger/debuggermanager.cpp

@@ -860,6 +860,7 @@ void DebuggerManager::cleanupViews()
     threadsHandler()->removeAll();
     modulesHandler()->removeAll();
     watchHandler()->cleanup();
+    registerHandler()->removeAll();
     m_sourceFilesWindow->removeAll();
 }