Bug: Generation of MetaModel instance breaks when no declarations

[jeromesimeon]

If there're no declarations in the concerto cto file, the metamodel generation throws and error instead of creating a metamodel with no declarations.

How to reproduce

namespace foobar

[jeromesimeon]

This is only when fully qualified name resolution is being used:

zsh-5.8$ ../concerto-cli/index.js import --input test/data/model/empty.cto
11:40:52 AM - INFO: {
  "$class": "concerto.metamodel.ModelFile",
  "namespace": "test.empty",
  "imports": []
}
zsh-5.8$ ../concerto-cli/index.js import --input test/data/model/empty.cto --resolve
11:41:00 AM - ERROR: Cannot read property 'forEach' of undefined