VEXIRSBConveter: Fix two places where regs do not have tags. #468

Job	Run time
ci / Build	3m 54s
windows / Test Windows	25s
macos / Test macOS	16s
ci / Lint	1m 20s
ci / Test (0)	4m 19s
ci / Test (1)	5m 37s
ci / Test (2)	7m 22s
ci / Test (3)	9m 1s
ci / Test (4)	6m 24s
ci / Test (5)	8m 49s
ci / Test (6)	4m 55s
ci / Test (7)	4m 53s
ci / Test (8)	5m 56s
ci / Test (9)	6m 10s
ci / Publish Unit Tests Results	1s
	1h 9m 22s

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