[media] add feedback to dropdown field when is empty

[shonibare]

Fixes #7951

[ridz1208]

not exactly how I was expecting the placeholder to behave. it shows up as an actual option not a place holder. @driusan im on the fence about this but functionally it works.

[driusan]

@ridz1208 how are you expecting a placeholder for a dropdown to work?

[ridz1208]

Like a placeholder

[ridz1208]

Issue found (see screenshots)

To reproduce on RB:

1. go to the upload form
2. select candidate DCC090 + V2 + AOSI
3. change candidate to DCC355
4. ERROR

to reproduce without RB:
try choosing a candidate which has visits and a visit and an instrument then try selecting a candidate which doesn't have any visits

[shonibare]

Issue found (see screenshots)

To reproduce on RB:

1. go to the upload form
2. select candidate DCC090 + V2 + AOSI
3. change candidate to DCC355
4. ERROR

to reproduce without RB: try choosing a candidate which has visits and a visit and an instrument then try selecting a candidate which doesn't have any visits

Error fixed