Guard single-corner geometry smoothing against missing portal neighbors

[Copilot]

Selecting a wall corner and applying geometry hotkeys could throw a NullReferenceException inside EditorActions.EditSectorGeometry. The failure came from the single-corner smoothing path assuming portal/boundary neighbor lookups always returned a valid RoomSectorPair.

• Problem

  • Single-corner smoothing dereferenced originSector / cornerSectors without validating that the portal lookup resolved to a real room-sector pair.
  • This could fail on wall selections near boundaries or non-resolvable adjoining sectors.

• Change

  • Added null-safe handling for the single-corner smoothing branch in EditSectorGeometry.
  • If the origin lookup is invalid, the corner comparison is skipped entirely.
  • If an individual neighboring corner lookup is invalid, that corner is treated as non-matching instead of crashing.

• Implementation detail

  • Extracted the corner height comparison into a small local helper to make the validity check explicit and keep the smoothing branch readable.

bool IsCornerValidAndAtSameHeight(RoomSectorPair cornerSector, SectorEdge edge, SectorVerticalPart cornerVertical, int referenceHeight)
{
    if (cornerSector.Sector == null || cornerSector.Room == null)
        return false;

    return referenceHeight == cornerSector.Sector.GetHeight(cornerVertical, edge) + cornerSector.Room.Position.Y;
}

[Nickelony]

@copilot Would you be able to provide reproduction steps for the original issue? What do we have to do in order to get the original error before the fix was applied? Also, please double-check that the changes don't cause any regressions for other places in the code.

[Copilot]

@copilot Would you be able to provide reproduction steps for the original issue? What do we have to do in order to get the original error before the fix was applied? Also, please double-check ...

Most likely repro before f166289 was:

1. Open the editor in Geometry mode.
2. Select a single wall sector that sits on a room boundary or on a wall portal where one diagonal neighbor lookup can fall outside the room / into a missing adjoining sector.
3. Click the same selection with Ctrl until the selection arrow becomes a single corner (CornerNW/NE/SE/SW).
4. Trigger a smooth geometry hotkey on that selection: Alt+Q / Alt+A for floor, or Alt+W / Alt+S for ceiling.

That path goes through GenericDirectionalControlCommand() into EditSectorGeometry(..., smooth: true). Before the fix, the single-corner smoothing block dereferenced originSector and cornerSectors[i] without checking whether GetSectorTryThroughPortal() had returned a valid room/sector pair, which is what caused the null reference.

I also re-checked the regression scope on f166289: the change only affects the area.Width == -1 && area.Height == -1 && arrow > ArrowType.EdgeW smooth single-corner case. Non-smooth edits, edge smoothing, and multi-sector smoothing are unchanged. For valid neighbors the height comparison is the same as before; only invalid portal/boundary lookups now short-circuit, which matches the null-safe behavior already used elsewhere in the smoothing code.

[Nickelony]

Managed to replicate it:

Simply CTRL+Click on room boundary wall like this:

Then when you see the X, press ALT+Q and it crashes.

This PR has actually fixed it.

[Copilot]

Pull request overview

Guards the geometry smoothing logic in EditorActions.EditSectorGeometry so single-corner smoothing no longer crashes when portal/boundary neighbor sector lookups fail, improving editor stability during corner-based geometry hotkeys.

Changes:

• Added null-safe handling when resolving the “origin” sector for single-corner smoothing.
• Added null-safe handling for each corner-neighbor sector comparison via a small local helper.

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