small bug in webfs - without it I get aborts on a PHP based site I use.

Reference: /n/sources/patch/applied/webfs-base
Date: Mon Aug  3 14:00:07 CES 2009
Signed-off-by: steve@quintile.net

--- /sys/src/cmd/webfs/url.c	Mon Aug  3 13:56:02 2009
+++ /sys/src/cmd/webfs/url.c	Mon Aug  3 13:55:59 2009
@@ -261,7 +261,7 @@
 	pdest = dest;
 
 	/* 6a: start with base, discard last segment */
-	if(base){
+	if(base && base[0]){
 		/* Empty paths don't match in our scheme; 'base' should be nil */
 		assert(base[0] == '/');
 		e = strrchr(base, '/');