No user feedback when connection to the server failed

[bertrandboudaud]

Describe the bug
User feedback is expected when something goes wrong. in that case, the log displays an error but is expected that the error is displayed in the info panel as most of the errors are.
as part of this bug, or it could be a separate issue, the dialog box stays frozen for some long seconds, it is expected that the ui does not freeze.

To Reproduce
Steps to reproduce the behavior:

1. Create a new session with some example (HPLC_UV_Unknown)
2. Click on Action > Run Workflow
3. Click on run on Server
4. fill settings with random data
5. run workflow
6. the UI is frozen for a time
7. The dialog box closes
8. No error is displayd, only on log

Expected behavior
It is expected that the error is displayed in the info panel as most of the errors are.
as part of this bug, or it could be a separate issue, the dialog box stays frozen for some long seconds, it is expected that the UI does not freeze.

Screenshots

Version information
master branch, c0507d4