Merge branch '3018-search-background' into 'master'

Fix top app bar background in OLED black theme

Closes #3019

See merge request fdroid/fdroidclient!1559

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

@@ -10,6 +10,7 @@
     <com.google.android.material.appbar.AppBarLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
+        android:background="@android:color/transparent"
         android:fitsSystemWindows="true">
 
         <LinearLayout