Fixed compilation warnings

[radarhere]

https://github.com/python-pillow/Pillow/actions/runs/4571913703/jobs/8070643875#step:7:66

src/_imaging.c: In function ‘getink’:
src/_imaging.c:555:44: warning: ‘tupleSize’ may be used uninitialized in this function [-Wmaybe-uninitialized]
555 | if (tupleSize != 1 && tupleSize != 2) {
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

This variable was added in #7010.

[radarhere]

Compiling on my macOS machine, I see

src/libImaging/Quant.c:344:17: warning: variable 'nLeft' set but not used [-Wunused-but-set-variable]
int nRight, nLeft;
^
1 warning generated.

This is because nLeft is only used if NO_OUTPUT is defined. I've added a commit to also only set nLeft if NO_OUTPUT is defined.