How to reproduce

• connect to cms
• open tags module
• click on add a tag
• uncheck the checkbox to be able to set a key
• enter some spaces in the key
• set the title of the tag
• click on OK

Actual behavior

• the tag is added with a key containing only spaces

Expected behavior

• a ! is displayed in front of the key due to the spaces
• the tag is rejected when I click on OK

*Another problem
Some time I got a ! in front of the key when I open the pop-up to add a tag, the ! is displayed before any action from me. It is the one about the key.