ThemeManager::ReloadMetrics: only reload metrics, not the whole theme. This

is much less unintrusive, and fixes crashes on most "retry" theme dialogs due
to reloading and resetting Lua and other things unexpectedly in the middle of
a screen load.

stepmania/src/ThemeManager.cpp

@@ -681,12 +681,8 @@ bool ThemeManager::HasMetric( const CString &sClassName, const CString &sValueNa
 void ThemeManager::ReloadMetrics()
 {
 	// force a reload of the metrics cache
-	const CString sThemeName = m_sCurThemeName;
-	const CString sCurLanguage = m_sCurLanguage;
-	m_sCurThemeName = "";
-	m_sCurLanguage = "";
+	LoadThemeMetrics( g_vThemes, m_sCurThemeName, m_sCurLanguage );
 
-	SwitchThemeAndLanguage( sThemeName, sCurLanguage );
 	if( SCREENMAN )
 		SCREENMAN->SystemMessage( "Reloaded metrics" );