Do not ignore a detected patchfile brokenness.

find_header() function is used to read and parse the patchfile
and it detects errors in the patch, but one place ignored the
error and went ahead, which was quite bad.

Noticed by Jeff Garzik.

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-apply.c

@@ -812,7 +812,7 @@ 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;
-			error("patch fragment without header at line %d: %.*s", linenr, (int)len-1, line);
+			return error("patch fragment without header at line %d: %.*s", linenr, (int)len-1, line);
 		}
 
 		if (size < len + 6)