Corrupt ldraw.org updates page caused LDView crash

[tcobbs]

Describe the bug
The updates list on ldraw.org was temporarily returning invalid data. This caused LDView's check for updates/install LDraw library functionality to fail.

To Reproduce
Steps to reproduce the behavior:
Have LDView parse the following line from the LDraw updates URL:

COMPLETE	2026-01	2026-01-29	ZIP	/storage/library/updates/complete.zip	134742141	6aae0bba9174235d725ff1ea8b7f6b7f

The 5th column is presumed to be the cause of the crash.

Expected behavior
Even if ldraw.org provides LDView with invalid data, LDView should not crash. It should instead show an error message.

Platform (please complete the following information):

• OS: All

Additional context
Add any other context about the problem here.

[tcobbs]

The code needs to make sure urlScheme is not NULL on the following line before calling isSupportedURLScheme :

ldview/TCFoundation/TCWebClient.cpp

Line 1341 in 78d549d

if (plugin != NULL && plugin->isSupportedURLScheme(urlScheme))