Check return value of 'virtual bool QFile::open(QIODeviceBase::OpenMode)'

Signed-off-by: Dylan Schooner <dschooner05@gmail.com>

launcher/Application.cpp

@@ -1968,7 +1968,9 @@ bool Application::handleDataMigration(const QString& currentData,
 
     auto setDoNotMigrate = [&nomigratePath] {
         QFile file(nomigratePath);
-        file.open(QIODevice::WriteOnly);
+        if (!file.open(QIODevice::WriteOnly)) {
+            qWarning() << "setDoNotMigrate failed; Failed to open file '" << file.fileName() << "' for writing!";
+        }
     };
 
     // create no-migrate file if user doesn't want to migrate