Fix 3 problems with `plSubWorldMsg`. #2417

Job	Run time
linux-x64-internal-release	11m 27s
macos-x64-internal-release	24m 27s
linux-x64-internal-debug	7m 53s
Check for Max SDK	1s
macos-x64-internal-debug	17m 17s
linux-x64-external-release	10m 0s
macos-x64-external-release	25m 48s
maxplugin-${{ matrix.cfg.str }}-${{ matrix.cfg.sdk-version }}	0s
windows-x86-internal-release	18m 26s
windows-x86-internal-debug	16m 6s
windows-x86-external-release	21m 27s
windows-x64-internal-release	17m 38s
windows-x64-internal-debug	14m 3s
windows-x64-external-release	17m 17s
	3h 21m 50s

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