Make VEXExprConverter more resilient #300

Job	Run time
docs	17s
macos / Test macOS	18s
windows / Test Windows	33s
ci / Build	7m 2s
ci / Lint	1m 13s
ci / Test (0)	8m 39s
ci / Test (1)	10m 2s
ci / Test (2)	5m 19s
ci / Test (3)	9m 43s
ci / Test (4)	6m 3s
ci / Test (5)	11m 48s
ci / Test (6)	6m 3s
ci / Test (7)	9m 53s
ci / Test (8)	4m 59s
ci / Test (9)	6m 36s
ci / Publish Unit Tests Results	1s
	1h 28m 29s

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