Fixed up some issues

Fixed up a few issues with the UniRF Remix app.

These include the blank screen when loading the app from Favorite App shortcut, and also fixed the app from freezing after a signal is sent if buttons were pressed during the send process.

Note: Freezing during a send still occurs but it should no longer hard lock the Flipper Zero.

More Error Checking!

Added more error checking in this release. The app will verify that the values of universal_rf_map are existing, but also the definitions in the map are actual files and are readable.

This doesn't change the fact that only RAW captures are supported at the moment. Nothing else has been added or removed.

Initial Release

Initial release of the UniRF Remix app for Flipper Zero