cubicweb-collaboration #4389860 Crash when migrating final applications that do not use 'frozen' [validation pending]

1.0.0_Any.py crashes => protect using getattr

prioritynormal
typebug
done in1.0.1
load0.100
load left0.000
closed by#826bc1e11ab8 [migration] Use getattr for frozen attribute in 1.0.0 migration
patch[migration] Use getattr for frozen attribute in 1.0.0 migration [applied]