Fix inefficient baseDir non-empty check

There's no need to call a string function and have function call
overhead if you remember how C strings work: they have a null
terminator. So if the first char in a string is a null terminator, then
the string is completely empty. So you don't need to call that function.

desktop_version/src/FileSystemUtils.cpp

@@ -45,7 +45,7 @@ int FILESYSTEM_init(char *argvZero, char* baseDir, char *assetsPath)
 	PHYSFS_permitSymbolicLinks(1);
 
 	/* Determine the OS user directory */
-	if (baseDir && strlen(baseDir) > 0)
+	if (baseDir && baseDir[0] != '\0')
 	{
 		strcpy(output, baseDir);