fix some stale StepsID entries hang around after unloading edits

stepmania/src/SongManager.cpp

@@ -1225,6 +1225,9 @@ void SongManager::FreeAllLoadedFromProfiles()
 		Song* pSong = m_pSongs[s];
 		pSong->FreeAllLoadedFromProfiles();
 	}
+
+	// After freeing some Steps pointers, the cache will be invalid.
+	SongID::ClearCache();
 }
 
 static bool CheckPointer( const Song *p )

stepmania/src/StepsUtil.cpp

@@ -195,9 +195,8 @@ XNode* StepsID::CreateNode() const
 }
 
 
-void StepsID::Invalidate( Song *pStaleSong )
+void StepsID::ClearCache()
 {
-	// FIXME: Only flush entries with the stale song
 	g_Cache.clear();
 }
 

stepmania/src/StepsUtil.h

@@ -39,7 +39,7 @@ public:
 	void LoadFromNode( const XNode* pNode );
 	CString ToString() const;
 	bool IsValid() const;
-	static void Invalidate( Song *pStaleSong );
+	static void ClearCache();
 };
 
 #endif