CiviCRM Import does not check for non-integer data when importing to integer fields

To reproduce.

Create a custom data field with a "integer" data type and associate with individual contacts.

Create an import file with firstname and lastname of contact, with data to be mapped to the custom field...put non integer data in the field, e.g. "10 01"

Upload, CivCRM Import will report 1 contact to import, but when it tries to import on the next stage it will break.

Developer who is fixing this issue, may want to investigate if there are any other data type mismatch scenarios which could break the import process.