Default constructor of ResourceKey creates zero key.
Default constructor of ResourceKey creates zero key.

When resource access later fails on not loaded data, zero key in
assertion message might hint that the Resource instance was
default-constructed and thus not loaded at all.

MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum,ashimidashajia/magnum,DerThorsten/magnum,DerThorsten/magnum,ashimidashajia/magnum,ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum