[pty] Fix missing `or` #604

Job	Run time
make (check, cppflags=-DVM_CHECK_MODE)	8m 26s
make (check, i686)	10m 53s
make (check, --disable-yjit)	7m 12s
make (check, --enable-shared --enable-load-relative)	7m 20s
make (test-bundler-parallel)	23m 14s
make (test-bundled-gems)	17m 53s
make (check, ubuntu-20.04)	8m 55s
Ubuntu result	1s
	1h 23m 54s

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