don't read the metric before ThemeManager is loaded

stepmania/src/ThemeManager.h

@@ -30,6 +30,7 @@ public:
 	void SwitchThemeAndLanguage( const CString &sThemeName, const CString &sLanguage );
 	void UpdateLuaGlobals();
 	CString GetCurThemeName() { return m_sCurThemeName; };
+	bool IsThemeLoaded()	{ return !m_sCurThemeName.empty(); };
 	CString GetCurLanguage() { return m_sCurLanguage; };
 	CString GetCurThemeDir() { return GetThemeDirFromName(m_sCurThemeName); };
 	void NextTheme();

stepmania/src/ThemeMetric.h

@@ -62,7 +62,7 @@ public:
 
 	void Read()
 	{
-		if( m_sName != "" )
+		if( m_sName != ""  &&  THEME  &&   THEME->IsThemeLoaded() )
 			THEME->GetMetric( m_sGroup, m_sName, m_currentValue );
 	}