Start/Stop Tx buttons not enabled in stream list window when stream file opened

[pstavirs]

Precondition:
No streams are configured, Start/Stop Tx buttons disabled in stream list window

Trigger:
Open a stream file

Expected:
Start/Stop Tx buttons get enabled

Actual:
Start/Stop Tx buttons remain disabled, until one (or more) streams are selected. This behaviour has a potential to indicate (incorrectly) that only selected streams are transmitted when clicking start Tx.

Problem is not seen when creating a new stream or pasting a stream