Should the initializer work with nil as a phone_number?

[meceo]

Perhaps we should allow the initializer to work with nil value as a phone number. Current behavior raises an exception "NoMethodError: undefined method `sub' for nil:NilClass". That requires a user of the model to always check if the phone number isn't nil. However, when an empty string is provided a user can call msisdn.valid? to check whether a model is valid without wondering about the reasons (invalid due to phone number being nil or because of something else)

dovecote/app/models/dovecote/msisdn.rb

Line 208 in a5870b4

phone_number = phone_number

change proposition:
phone_number = phone_number.to_s.sub...(etc)