Creating a new Event Command without a name results in a stack trace rather than an error

[cgibbons]

To recreate:
1. Navigate to Event Manager
2. Navigate to the Commands tab
3. Press the Add button but do not enter anything in the text field next to it.
4. Note stack trace.

Stack trace is:

Type: BadRequest

Value: ('Empty or invalid id specified', )

Traceback (innermost last):

• Module ZPublisher.Publish, line 114, in publish
• Module ZPublisher.mapply, line 88, in mapply
• Module ZPublisher.Publish, line 40, in call_object
• Module Products.ZenEvents.EventManagerBase, line 2126, in manage_addCommand
• Module Products.ZenRelations.ToManyContRelationship, line 102, in _setObject
• Module Products.ZenRelations.ToManyContRelationship, line 93, in addRelation
• Module Products.ZenRelations.RelationshipBase, line 81, in addRelation
• Module Products.ZenRelations.ToManyContRelationship, line 156, in _add
• Module OFS.ObjectManager, line 63, in checkValidId

BadRequest: ('Empty or invalid id specified', )

[kkearney]

(In [11336]) * Refs #3032: catch bad input.

[kkearney]

(In [11338]) * Fixes #3032: catch bad input. Reviewed by JP