Fix strip blank space for empty string

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/parse.c b/parse.c
index afbde61..18e8a40 100644
--- a/parse.c
+++ b/parse.c
@@ -273,6 +273,8 @@
 {
 	char *s = *p;
 
+	if (!strlen(s))
+		return;
 	while (isspace((int) *s))
 		s++;
 
@@ -283,6 +285,9 @@
 {
 	char *start = p, *s;
 
+	if (!strlen(p))
+		return;
+
 	s = strchr(p, ';');
 	if (s)
 		*s = '\0';