Steps to reproduce
1. Create a segment group Private - private
2. Create segments: Finance - finance & Society - society.
3. Create a segment group Corporate - corporate
4. Create segment: Finance - finance

Result
No error message. After redirect to Segment Groups list 0 is present in the table instead of segments.

Expected result
A proper error message is displayed.

Note
After the second or third execution the following message popped-up in the error notification bar:

An exception occurred while executing 'INSERT INTO `ibexa_segments` (identifier, name) VALUES(?, ?)' with params ["finanzexperte", "Finanzexperte"]: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'finanzexperte' for key 'ibexa_segments_identifier'