[master] 8572a43 Skip processing empty strings earlier

[Federico G. Schwindt]

commit 8572a43523c45f02a892c56907c2c78e8d2e72c3
Author: Federico G. Schwindt <fgsch at lodoss.net>
Date:   Fri Apr 28 21:16:07 2017 -0700

    Skip processing empty strings earlier

diff --git a/bin/varnishd/cache/cache_vrt.c b/bin/varnishd/cache/cache_vrt.c
index a8100b3..c69914c 100644
--- a/bin/varnishd/cache/cache_vrt.c
+++ b/bin/varnishd/cache/cache_vrt.c
@@ -170,7 +170,7 @@ VRT_StringList(char *d, unsigned dl, const char *p, va_list ap)
 	b = d;
 	e = b + dl;
 	while (p != vrt_magic_string_end && b < e) {
-		if (p != NULL) {
+		if (p != NULL && *p != '\0') {
 			x = strlen(p);
 			if (b + x < e)
 				memcpy(b, p, x);