lazymanifest: don't crash when out of memory (issue5916) stable

lazymanifest: don't crash when out of memory (issue5916)

self->lines can be NULL if we failed to allocate memory for it.

--- a/mercurial/cext/manifest.c	Wed Jun 13 10:37:39 2018 -0400
+++ b/mercurial/cext/manifest.c	Wed Jun 13 10:41:20 2018 -0400
@@ -185,7 +185,7 @@
 {
 	/* free any extra lines we had to allocate */
 	int i;
-	for (i = 0; i < self->numlines; i++) {
+	for (i = 0; self->lines && (i < self->numlines); i++) {
 		if (self->lines[i].from_malloc) {
 			free(self->lines[i].start);
 		}