Fix "Do not ignore a detected patchfile brokenness."

Returning negative value from there does not stop the caller from using
the earlier part.

Noticed by Linus.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

builtin-apply.c

@@ -812,7 +812,8 @@ static int find_header(char *line, unsigned long size, int *hdrsize, struct patc
 			struct fragment dummy;
 			if (parse_fragment_header(line, len, &dummy) < 0)
 				continue;
-			return error("patch fragment without header at line %d: %.*s", linenr, (int)len-1, line);
+			die("patch fragment without header at line %d: %.*s",
+			    linenr, (int)len-1, line);
 		}
 
 		if (size < len + 6)