Fix crash on usb disconnect, fix hiding of main window

[DonLakeFlyer]

• Fix QGC crashes after disconnecting USB [Release V5.0] #12858
• Fixes crash on usb cable disconnect
• Fixes main window disappearing on active vehicle going away
• Fixes link errors showing message in title and title in message area
• Stops popping link error dialog on usb cable pull
• Replacement for QML: Fix Accidental Hiding of Main Window #12860

[Copilot]

Pull Request Overview

This PR resolves multiple issues including crashes on USB cable disconnect, unexpected main window disappearance when the active vehicle changes, and incorrect link error dialogs.

• Fallback to an offline editing vehicle when activeVehicle is null
• Removal of redundant activeVehicle change connections in QML
• Updates to SerialLink error handling for USB disconnects and a dedicated communication error handler in LinkManager

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

File	Description
src/QmlControls/FactValueGrid.cc	Adds a fallback for activeVehicle to use offlineEditingVehicle
src/FlightDisplay/FlyViewMap.qml	Removes Connections blocks handling activeVehicle changes
src/Comms/SerialLink.cc	Handles ResourceError with fallthrough to PermissionError logic
src/Comms/LinkManager.h & LinkManager.cc	Introduces a dedicated _communicationError handler and connection

Comments suppressed due to low confidence (1)

src/Comms/LinkManager.h:127

• [nitpick] Consider clarifying the parameter names to better reflect their usage (e.g., swapping or renaming them) to match the order of arguments in the showAppMessage() call.

void _communicationError(const QString &title, const QString &error);

[DonLakeFlyer]

@rubenp02 I could see why those two Connections blocks were needed. There was already activeVehicle checking in other places on the goto location item. I also tested the vehicle going away while a goto location was displayed and it correctly went away.

[DonLakeFlyer]

• Stops popping link error dialog on usb cable pull

@HTRamsey This didn't happen in pre-5.0 builds. It's kinda annoying. Not sure what you think about this change.

[HTRamsey]

@DonLakeFlyer yeah that's fine. I kinda wish we had a separate notification message that just kinda pops up and fades out after a few seconds, particularly for things like this that the user should notice but doesn't require actual input to dismiss it.

[HTRamsey]

I believe that change in FactValueGrid should fix these warnings too right? It'll be the offline vehicle instead of null now I think

[DonLakeFlyer]

I believe that change in FactValueGrid should fix these warnings too right?

The second one. But not GuidedActionsController

I'm going to merge this because without it the main window close thing makes testing really hard!