Fix check buffer not alloc'd

lib/runtime.c

@@ -17,6 +17,7 @@ char * readString() {
 	char *line = NULL;
 	size_t bufLen = 0;
 	getline(&line, &bufLen, stdin);
+	if (!line) error();
 	size_t len = 0;
 	while (line[len]) len++;
 	line[len-1] = 0;