TR2X bug: the assault course timer doesn't pause when the inventory is open

[aredfan]

Regression since: 0.6

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The OG behaviour is the assault course timer is paused when the inventory is open.

Steps to reproduce:

1. play Lara's Home
2. trigger the assault course timer
3. open the inventory and wait for 10 seconds or so
4. close the inventory
5. the timer has continued

It's worth noting that the stopwatch's hands don't move in Lara's Home, whereas the stopwatch's hands do move in the story levels.