GH_* ports: Malformed conditional (${DISTNAME:Nextra-cmake-modules-*})

Hi porters,

in ports that use the kf5 module and have only set GH_*, I get the
following message.

For example:

GH_ACCOUNT = ksnip
GH_PROJECT = ksnip
GH_TAGNAME = v1.8.0

MODULES = devel/kf5

$ make configure
*** Parse error in /usr/ports/graphics/ksnip: Malformed conditional (${DISTNAME:Nextra-cmake-modules-*}) (/usr/ports/devel/kf5/kf5.port.mk:9)
*** Parse error: Missing dependency operator (/usr/ports/devel/kf5/kf5.port.mk:9)

Is DISTNAME perhaps not set at that point? Any idea how to fix it
cleanly? This check is important for the module, of course.

Cheers,

Rafael