Piwik\Plugin\Manager::deactivateThemeIfTheme PHP Method

    private function deactivateThemeIfTheme($pluginName)
    {
        // Only one theme enabled at a time
        $themeEnabled = $this->getThemeEnabled();
        if ($themeEnabled && $themeEnabled->getPluginName() != self::DEFAULT_THEME) {
            $themeAlreadyEnabled = $themeEnabled->getPluginName();
            $plugin = $this->loadPlugin($pluginName);
            if ($plugin->isTheme()) {
                $this->deactivatePlugin($themeAlreadyEnabled);
            }
        }
    }