do not segfault if make_cache_entry failed

Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
diff --git a/builtin-reset.c b/builtin-reset.c
index c24c219..16e6bb2 100644
--- a/builtin-reset.c
+++ b/builtin-reset.c
@@ -121,6 +121,9 @@
 			struct cache_entry *ce;
 			ce = make_cache_entry(one->mode, one->sha1, one->path,
 				0, 0);
+			if (!ce)
+				die("make_cache_entry failed for path '%s'",
+				    one->path);
 			add_cache_entry(ce, ADD_CACHE_OK_TO_ADD |
 				ADD_CACHE_OK_TO_REPLACE);
 		} else