We should improve error messages

We sometimes get messages such as « The required field '' is empty! », we should avoid this as much as possible.

(from redmine: issue id 5137, created on 2016-09-05, closed on 2016-12-05)

• Relations:
  • duplicates #4820
  • duplicates #4805
• Changesets:
  • Revision 39683c03 by Côme Chilliet on 2016-09-05T14:23:02.000Z:

Fixes #5137 Improving error messages

• Revision eb74a7f0 by Côme Chilliet on 2016-11-18T17:20:58.000Z:

Fixes #5137 Improving error messages

• Custom Fields:
  • Bug in version: 1.0.14
  • Support contract: None