Brightness management in DisplayApp : do not allow the brightness level OFF when loading app and going to running mode. Such issue could occur in case of inconsistent or corrupted settings.

src/displayapp/DisplayApp.h

@@ -121,6 +121,7 @@ namespace Pinetime {
       Apps nextApp = Apps::None;
       DisplayApp::FullRefreshDirections nextDirection;
       System::BootErrors bootError;
+      void ApplyBrightness();
     };
   }
 }