replaced hard coded background color with coresponding color-definition

res/layout/file_details_empty.xml

@@ -20,7 +20,7 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	android:layout_width="match_parent"
 	android:layout_height="match_parent"
-    android:background="#F7F7F7"
+    android:background="@color/background_color"
     android:orientation="vertical">
 
     <TextView