fix: do not apply system theme on launch

Closes PrismLauncher/PrismLauncher#490

Regression introduced by PrismLauncher/PrismLauncher#249

Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>

launcher/Application.h

@@ -120,7 +120,7 @@ public:
 
     void setIconTheme(const QString& name);
 
-    void applyCurrentlySelectedTheme();
+    void applyCurrentlySelectedTheme(bool initial = false);
 
     QList<ITheme*> getValidApplicationThemes();