cleanup: Don't savestatsandsettings if filesystem not init

This isn't necessary, but it does silence these annoying logs if you
pass an invalid argument or don't have data.zip:

    [ERROR] Could not get window size: Invalid renderer
    [WARN] Stats not loaded! Not writing unlock.vvv.
    [ERROR] Could not get window size: Invalid renderer
    [WARN] Settings not loaded! Not writing settings.vvv.

To do this, I've added FILESYSTEM_isInit().

desktop_version/src/FileSystemUtils.cpp

@@ -186,6 +186,11 @@ int FILESYSTEM_init(char *argvZero, char* baseDir, char *assetsPath)
     return 1;
 }
 
+bool FILESYSTEM_isInit(void)
+{
+    return isInit;
+}
+
 static unsigned char* stdin_buffer = NULL;
 static size_t stdin_length = 0;