Set default visibility of restart button to GONE

This fixes the issue that button still shows when installation fails.

Author: aviraxp

app/src/main/res/layout/fragment_flash_md2.xml

@@ -39,7 +39,7 @@
 
         <com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton
             android:id="@+id/restart_btn"
-            gone="@{viewModel.flashing || !viewModel.showReboot}"
+            android:visibility="gone"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity="bottom|end"