Disable/enable menu actions depending on what currently can be done.

src/gui/DatabaseWidget.cpp

@@ -185,6 +185,11 @@ void DatabaseWidget::switchToMasterKeyChange()
     setCurrentIndex(3);
 }
 
+void DatabaseWidget::setCurrentIndex(int index) {
+    QStackedWidget::setCurrentIndex(index);
+    Q_EMIT currentIndexChanged(index);
+}
+
 bool DatabaseWidget::dbHasKey()
 {
     return m_db->hasKey();