Checking entity by model name (cherry picked from: https://github.com/paupauorg/rails-erd/commit/34ed93ea7a8b54175250f41f2bdbbcaa6cbff9d4)
Checks that a model is not abstract before all (cherry picked from: https://github.com/burisu/rails-erd/commit/a287f3682776f0503d8be083352eecc288dda761)
Correct 'No entities found' error (cherry picked from: https://github.com/phlegx/rails-erd/commit/49448a35579bf50e3b2a0fc08fdb334d0d8a3909)