No error displayed when running workflow on server

[bertrandboudaud]

Describe the bug
There is no user feedback when running workflow while nothing is specified by the user.

To Reproduce
Steps to reproduce the behavior:

1. Create a new session with data (For example, HPL_UV_unknown example)
2. Click on Action > run workflow
3. Click on Run on server (no sign in, no server setup)
4. Click on Run Workflow
5. nothing happens, no error in logs

Expected behavior
We can expect that either the run workflow button is disabled, or a message popup. It can also go into the info panel, where other errors are displayed, usually. The log should display an error (only logs is not sufficient, user has to get feedback)

Version information
master branch, c0507d4