let revdeps return a flattening empty list
let revdeps return a flattening empty list

this fixes the case where installing something gave
a stacktrace showing "got Any but expected Bone"
or something similar
moznion/panda,TimToady/panda,tadzik/panda,tadzik/panda,sjn/panda,nbrown/panda,jonathanstowe/panda,will-crawford/panda,sjn/panda,niner/panda,laben/panda,perlpilot/panda,raydiak/panda,stmuk/panda,jonathanstowe/panda,skaji/panda,shoichikaji/panda,stmuk/panda,TimToady/panda,masak/panda,tadzik/panda,shoichikaji/panda,perlpilot/panda,hoelzro/panda,hoelzro/panda,hoelzro/panda,niner/panda,raydiak/panda,timo/panda,skaji/panda,masak/panda,sjn/panda,laben/panda,moznion/panda,will-crawford/panda,nbrown/panda,timo/panda