Check gnus-newsgroup-dependencies is hash table in gnus-id-to-thread

* lisp/gnus/gnus-sum.el (gnus-id-to-thread): If dependencies haven't
  been initialized yet, don't blow up. Mimicks previous (non hasht
  table) behavior.
1 job for master in 49 minutes and 53 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #1171
test-all

00:49:53

 
Name Stage Failure
failed
test-all Test
Makefile:313: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:288: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:962: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1