Fix incorrect print fragment background color (when loading)

Author: LunarX

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

@@ -40,7 +40,7 @@
     <FrameLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:background="@color/background"
+        android:background="@color/backgroundColor"
         tools:visibility="gone">
 
         <ProgressBar