don't recreate the resolv.conf file from the dhcp script if no dhcp server is supplied (reported by exobyte)

git-svn-id: svn://svn.openwrt.org/openwrt/branches/buildroot-ng/openwrt@4903 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/base-files/default/usr/share/udhcpc/default.script

@@ -38,12 +38,14 @@ case "$1" in
 			done
 		fi
 		
+		[ -n "$dns" ] && {
 			echo -n > $RESOLV_CONF
 			${domain:+echo search $domain} >> $RESOLV_CONF
 			for i in $dns ; do
 				echo "adding dns $i"
 				echo "nameserver $i" >> $RESOLV_CONF
 			done
+		}
 		
 		hotplug_event ifup