[4.0] 8795c23 Prevent a segmentation fault in VBE_AddBackend

[Dridi Boukelmoune]

commit 8795c23ecf20f1c789cbae4f13ca6ffa4aef23ca
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Mon Jan 11 12:46:06 2016 +0100

    Prevent a segmentation fault in VBE_AddBackend

diff --git a/bin/varnishd/cache/cache_backend_cfg.c b/bin/varnishd/cache/cache_backend_cfg.c
index a5d913f..5b122d0 100644
--- a/bin/varnishd/cache/cache_backend_cfg.c
+++ b/bin/varnishd/cache/cache_backend_cfg.c
@@ -192,6 +192,10 @@ VBE_AddBackend(struct cli *cli, const struct vrt_backend *vb)
 		CHECK_OBJ_NOTNULL(b, BACKEND_MAGIC);
 		if (strcmp(b->vcl_name, vb->vcl_name))
 			continue;
+		if ((vb->ipv4_suckaddr != NULL) ^ (b->ipv4 != NULL))
+			continue;
+		if ((vb->ipv6_suckaddr != NULL) ^ (b->ipv6 != NULL))
+			continue;
 		if (vb->ipv4_suckaddr != NULL &&
 		    VSA_Compare(b->ipv4, vb->ipv4_suckaddr))
 			continue;