luci-mod-freifunk: lua error accessing the "profile_expert" site and others

accessing ```/cgi-bin/luci/admin/freifunk/basics/profile_expert``` raises a lua error:

> ...r/lib/lua/luci/model/cbi/freifunk/profile_expert.lua:12: attempt to concatenate local 'community' (a boolean value)
stack traceback:
...r/lib/lua/luci/model/cbi/freifunk/profile_expert.lua:12: in function 'func'
/usr/lib/lua/luci/cbi.lua:66: in function 'load'
/usr/lib/lua/luci/dispatcher.lua:1336: in function '_cbi'
/usr/lib/lua/luci/dispatcher.lua:1019: in function 'dispatch'
/usr/lib/lua/luci/dispatcher.lua:479: in function

even ```uci get feifunk.community.name``` return a valid profile-suffix (here "berlin").

This probably relates to running it on the latest OpenWrt master:
> OPENWRT_REPO=https://git.openwrt.org/openwrt/openwrt.git
OPENWRT_COMMIT=ad27c133eb606ee39fa346b7bdb26c1764ee869e
PACKAGES_PACKAGES_REPO=https://github.com/openwrt/packages.git
PACKAGES_PACKAGES_COMMIT=10fb31451e18b6a03f8070eeae373d37855ccc09
PACKAGES_LUCI_REPO=https://github.com/openwrt/luci.git
PACKAGES_LUCI_COMMIT=a573da0d191e30ccabc15b84fdc73f9b570fcf51