fixed

include/libmu/parse_mount.h

@@ -63,7 +63,9 @@ unsigned long mu_parse_opts(char *str, char *data, const size_t data_size) {
 		token = strtok(NULL, ",");
 	}
 
-	data[data_len - 1] = '\0';
+	if (data_len > 0)
+		data[data_len - 1] = '\0';
+
 	return opt;
 }