Clarify compiler-pacifier in frame.c

* src/frame.c (Fx_parse_geometry): Pacify the compiler in a
different way, so that the human reader can more easily see
that the initializations are unnecessary.
1 job for master in 64 minutes and 53 seconds (queued for 4 seconds)
Status Job ID Name Coverage
failed #3110


Name Stage Failure
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1