Fix bytecode optimization typo

Problem reported by Simon Frankau (Bug#35562).
* src/bytecode.c (exec_byte_code): Fix typo when optimizing varset.
1 job for master in 50 minutes and 39 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #1643
test-all

00:50:39

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:315: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:290: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1