nx-match: Avoid null pointer dereference in nx_pull_header__() error case.

Found by LLVM scan-build.

Reported-by: Kevin Lo <kevlo@FreeBSD.org>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>

diff --git a/lib/nx-match.c b/lib/nx-match.c
index 4b72460..21f291c 100644 (file)
--- a/lib/nx-match.c
+++ b/lib/nx-match.c
@@ -319,7 +319,9 @@ bad_len:
                 b->size);
 error:
     *header = 0;
-    *field = NULL;
+    if (field) {
+        *field = NULL;
+    }
     return OFPERR_OFPBMC_BAD_LEN;
 }