Fix misleading  message in Update Metadata Form.

First you put some data to Other field.
In next step you delete it.
Then you give message 'invalid key name'.
This is inconsistent to this field behavior.

DocImpact
Closes-Bug: #1371230

Change-Id: I61d3569adf89277ddec61507bd7816513e4623eb
Merge "Fix misleading  message in Update Metadata Form."