Remove theme data on theme deletion (#4529)

Credit to @DanHarrin. Fixes #1292.

modules/cms/classes/Theme.php

@@ -524,6 +524,19 @@ class Theme
         return ThemeData::forTheme($this);
     }
 
+    /**
+     * Remove data specific to this theme
+     * @return bool
+     */
+    public function removeCustomData()
+    {
+        if ($this->hasCustomData()) {
+            return $this->getCustomData()->delete();
+        }
+
+        return true;
+    }
+
     /**
      * Checks to see if the database layer has been enabled
      *

modules/cms/classes/ThemeManager.php

@@ -107,6 +107,8 @@ class ThemeManager
             throw new ApplicationException(trans('cms::lang.theme.delete_active_theme_failed'));
         }
 
+        $theme->removeCustomData();
+
         /*
          * Delete from file system
          */