Keep controller_load_check_arg() from crashing when filename doesn't contain '/'.

'slash' would be used uninitialized in this case. While we're here, change
code to use strrchr() instead of rolling our own and only stat() a filename if
we've found a '/', since we know 'extern->filename' will not contain a
directory name otherwise.

	modified:   controller/controller_load.c

controller/controller/controller_load.c

@@ -293,10 +293,12 @@ static char *rel2file(yyscan_t scanner, char *rel_name)
 		return NULL;
 
 	tmp = strdup(extra->filename);
-	for (ret = tmp; *ret; ret++)
-		if (*ret == '/')
-			slash = ret;
-	*slash = 0;
+	slash = strrchr(tmp, '/');
+	if (slash == NULL) {
+		free(tmp);
+		return NULL;
+	}
+	*slash = '\0';
 	asprintf(&ret, "%s/%s", tmp, rel_name);
 	free(tmp);