Explicitly set background for fragments

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/res/layout/file_details_sharing_menu_bottom_sheet_fragment.xml

@@ -25,6 +25,7 @@
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical"
+    android:background="@color/bg_default"
     android:paddingTop="@dimen/standard_padding">
 
     <LinearLayout

src/main/res/layout/send_share_fragment.xml

@@ -22,7 +22,8 @@
 <androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent"
+    android:background="@color/bg_default">
 
     <RelativeLayout
         android:layout_width="match_parent"