Use dark dialog for base theme picker

src/main/java/org/tasks/dialogs/DialogBuilder.java

@@ -24,6 +24,10 @@ public class DialogBuilder {
     }
 
     public AlertDialogBuilder newDialog() {
+        return newDialog(theme);
+    }
+
+    public AlertDialogBuilder newDialog(Theme theme) {
         return new AlertDialogBuilder(activity, theme, locale);
     }
 

src/main/java/org/tasks/dialogs/ThemePickerDialog.java

@@ -64,6 +64,10 @@ public class ThemePickerDialog extends InjectingDialogFragment {
             palette = (ColorPalette) savedInstanceState.getSerializable(EXTRA_COLOR_PALETTE);
         }
 
+        if (palette == ColorPalette.THEMES) {
+            theme = theme.withBaseTheme(themeCache.getThemeBase(2));
+        }
+
         final String[] themes = getResources().getStringArray(getNameRes());
 
         final boolean purchasedThemes = preferences.hasPurchase(R.string.p_purchased_themes);
@@ -90,7 +94,7 @@ public class ThemePickerDialog extends InjectingDialogFragment {
             }
         };
 
-        return dialogBuilder.newDialog()
+        return dialogBuilder.newDialog(theme)
                 .setAdapter(adapter, new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {

src/main/java/org/tasks/themes/Theme.java

@@ -23,6 +23,10 @@ public class Theme {
         this.themeAccent = themeAccent;
     }
 
+    public Theme withBaseTheme(ThemeBase themeBase) {
+        return new Theme(themeBase, themeColor, themeAccent);
+    }
+
     public ThemeBase getThemeBase() {
         return themeBase;
     }