Git: Fix warning when applying settings with Ok

The current parentDialog is the settings window, but it is closed
immediately, so the warning just disappears.

Change-Id: I7f5033239bf18e758595965587947bec40facf6f
Reviewed-by: hjk <hjk@qt.io>

src/plugins/git/gitplugin.cpp

@@ -87,6 +87,7 @@
 #include <QClipboard>
 #include <QFileDialog>
 #include <QMenu>
+#include <QTimer>
 #include <QVBoxLayout>
 
 #ifdef WITH_TESTS
@@ -477,8 +478,11 @@ void GitPluginPrivate::onApplySettings()
     bool gitFoundOk;
     QString errorMessage;
     m_settings.gitExecutable(&gitFoundOk, &errorMessage);
-    if (!gitFoundOk)
+    if (!gitFoundOk) {
+        QTimer::singleShot(0, this, [this, errorMessage] {
             Core::AsynchronousMessageBox::warning(tr("Git Settings"), errorMessage);
+        });
+    }
 }
 
 void GitPluginPrivate::cleanCommitMessageFile()