[FIX] mail_tracking: Changed injection method for 'failed_message_ids' field
[FIX] mail_tracking: Changed injection method for 'failed_message_ids' field

Before this commit, some methods with views crashes trying to
process 'failed_message_ids' field.
After this commit the 'failed_message_ids' field description
is properly generated.

OCA/social,OCA/social,OCA/social