Restore display tab on changing theme

app/src/main/java/eu/faircode/email/FragmentOptions.java

@@ -61,6 +61,10 @@ public class FragmentOptions extends FragmentBase {
     public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         TabLayout tabLayout = view.findViewById(R.id.tab_layout);
         tabLayout.setupWithViewPager(pager);
+
+        String tab = getActivity().getIntent().getStringExtra("tab");
+        if ("display".equals(tab))
+            pager.setCurrentItem(4);
     }
 
     private class PagerAdapter extends FragmentStatePagerAdapter {

app/src/main/java/eu/faircode/email/FragmentOptionsDisplay.java

@@ -280,6 +280,8 @@ public class FragmentOptionsDisplay extends FragmentBase implements SharedPrefer
         rgTheme.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(RadioGroup group, int checkedId) {
+                getActivity().getIntent().putExtra("tab", "display");
+
                 switch (checkedId) {
                     case R.id.rbThemeLight:
                         prefs.edit().putString("theme", "light").apply();