Fix setting background if change manualy dark theme (And remove duplication)

Signed-off-by: Joris Bodin <joris.bodin@infomaniak.com>

src/main/res/values-v21/styles.xml

@@ -24,12 +24,8 @@
         <item name="android:datePickerDialogTheme">@style/FallbackDatePickerDialogTheme</item>
     </style>
 
-    <style name="FallbackThemingTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+    <style name="FallbackThemingTheme" parent="FallbackThemingThemeBase">
         <item name="android:datePickerDialogTheme">@style/FallbackDatePickerDialogTheme</item>
-        <item name="android:textColor">@color/text_color</item>
-        <item name="android:textColorSecondary">@color/secondary_text_color</item>
-        <item name="colorSecondary">@color/secondary_text_color</item>
-        <item name="android:alertDialogTheme">@style/FallbackTheming.Dialog</item>
     </style>
 
     <style name="FallbackDatePickerDialogTheme" parent="Theme.MaterialComponents.DayNight.Dialog.Alert">

src/main/res/values/styles.xml

@@ -37,18 +37,18 @@
         <item name="android:textColorHint">@color/secondary_text_color</item>
     </style>
 
-	<style name="FallbackThemingTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
-		<item name="colorPrimary">#424242</item>
-		<item name="colorPrimaryDark">#212121</item>
-		<item name="colorAccent">#757575</item>
+    <style name="FallbackThemingThemeBase" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
         <item name="android:textAllCaps">false</item>
         <item name="android:textColor">@color/text_color</item>
         <item name="android:alertDialogTheme">@style/FallbackTheming.Dialog</item>
         <item name="dialogTheme">@style/FallbackTheming.Dialog</item>
         <item name="android:windowBackground">@color/bg_default</item>
         <item name="android:textColorSecondary">@color/secondary_text_color</item>
+        <item name="colorSecondary">@color/secondary_text_color</item>
     </style>
 
+    <style name="FallbackThemingTheme" parent="FallbackThemingThemeBase" />
+
 	<style name="FallbackDatePickerDialogTheme" parent="Theme.MaterialComponents.DayNight.Dialog.Alert">
         <item name="colorPrimary">@color/bg_default</item>
         <item name="android:textAllCaps">false</item>