When the host crashes, the error message is shown to the user. When startup fails, only a generic message is shown.
This adds the error message provided by the browser to aid debugging the problem.

• Sabotaged my browser host, got the icon crossed-out, got "native host not found" in the popup. There was no badge because the icon is crossed out already and the error never cleared
• Fixed my host, got normal plasma icon with generic popup icon (no behavior change)
• Killed my host, got a "!" badge with the error which was cleared when the popup was closed (no behavior change)