Fixed main theme

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

@@ -72,6 +72,8 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
         this.contacts = hasPermission(Manifest.permission.READ_CONTACTS);
 
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
+
+        if (!this.getClass().equals(ActivityMain.class)) {
             String theme = prefs.getString("theme", null);
             if ("system".equals(theme)) {
                 int uiMode = getResources().getConfiguration().uiMode;
@@ -83,6 +85,7 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
                 setTheme(R.style.AppThemeDark);
             else if ("black".equals(theme))
                 setTheme(R.style.AppThemeBlack);
+        }
 
         prefs.registerOnSharedPreferenceChangeListener(this);