quic: Fix "UNINIT" caught by coverity
quic: Fix "UNINIT" caught by coverity

In case of the model evolution mode has a obsolete or non-valid value,
just return, avoiding then the usage of non initalized variables.

Fantu/spice-common,SPICE/spice-common,fgouget/spice-common,fgouget/spice-common,fgouget/spice-common,Fantu/spice-common,elmarco/spice-common,elmarco/spice-common,elmarco/spice-common,elmarco/spice-common,freedesktop-unofficial-mirror/spice__spice-common,SPICE/spice-common,fgouget/spice-common,freedesktop-unofficial-mirror/spice__spice-common,SPICE/spice-common,Fantu/spice-common,Fantu/spice-common,freedesktop-unofficial-mirror/spice__spice-common,freedesktop-unofficial-mirror/spice__spice-common