background for settings screen

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/AndroidManifest.xml

@@ -215,7 +215,7 @@
         <activity
             android:name=".ui.activity.SettingsActivity"
             android:exported="false"
-            android:theme="@style/Theme.ownCloud" />
+            android:theme="@style/PreferenceTheme" />
         <activity
             android:name=".ui.preview.PreviewImageActivity"
             android:exported="false"

app/src/main/res/values/styles.xml

@@ -443,4 +443,11 @@
         <item name="android:id">@android:id/background</item>
         <item name="android:background">?android:attr/colorBackground</item>
     </style>
+
+    <style name="PreferenceTheme" parent="FallbackThemingTheme">
+        <item name="android:colorBackground">@color/bg_default</item>
+    </style>
+
+
+
 </resources>