Avoid use of QKeySequence::isEmpty in checks in command implementations.

isEmpty is the wrong thing to check when setting the default shortcut. In addition,
registering commands should not set their shortcut automatically (that
should be defined solely by the default shortcut and reading the
settings, which is done later).

src/plugins/coreplugin/modemanager.cpp

@@ -198,6 +198,9 @@ void ModeManager::objectAdded(QObject *obj)
     connect(cmd, SIGNAL(keySequenceChanged()), this, SLOT(updateModeToolTip()));
     for (int i = 0; i < d->m_modeShortcuts.size(); ++i) {
         Command *currentCmd = d->m_modeShortcuts.at(i);
+        // we need this hack with currentlyHasDefaultSequence
+        // because we call setDefaultShortcut multiple times on the same cmd
+        // and still expect the current shortcut to change with it
         bool currentlyHasDefaultSequence = (currentCmd->keySequence()
                                             == currentCmd->defaultKeySequence());
 #ifdef Q_WS_MAC