Add existing block creates a blank block

[trf000]

Adding an existing block submits the form below as a blank block with no title in addition to the existing block.

[trf000]

It seems that if an existing block is selected, layout add the block to that page, but the add existing block acts as a submit for the fields that follow and creates a new record. Either the forms need to somehow be separated into 2 forms or some logic disabling the insert if something is selected from the dropdown list.