miniupnpd: don't fail if IPv6 is not available at runtime (#12809)

git-svn-id: svn://svn.openwrt.org/openwrt/packages@35149 3c298f89-4303-0410-b956-a3cf2f4a3e73
miniupnpd: add missing patch from previous commit

git-svn-id: svn://svn.openwrt.org/openwrt/packages@35150 3c298f89-4303-0410-b956-a3cf2f4a3e73