attr: make it build with DEBUG_ATTR again

Commit 82dce99 (attr: more matching optimizations from .gitignore -
2012-10-15) changed match_attr structure but it did not update
DEBUG_ATTR-specific code. This fixes it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

attr.c

@@ -685,7 +685,7 @@ static int fill_one(const char *what, struct match_attr *a, int rem)
 
 		if (*n == ATTR__UNKNOWN) {
 			debug_set(what,
-				  a->is_macro ? a->u.attr->name : a->u.pattern,
+				  a->is_macro ? a->u.attr->name : a->u.pat.pattern,
 				  attr, v);
 			*n = v;
 			rem--;