Be more defensive regarding elements of 'load-history'

* lisp/loadhist.el (file-dependents):
* lisp/apropos.el (apropos-library):
* lisp/help-fns.el (help-fns--autoloaded-p, help--loaded-p):
* lisp/emacs-lisp/package.el (package--list-loaded-files):
Don't assume 'load-history' elements must have a string as their
'car'.  (Bug#34462)
1 job for master in 60 minutes and 1 second (queued for 1 second)
Status Job ID Name Coverage
failed #929


Name Stage Failure
test-all Test The script exceeded the maximum execution time set for the job
make -C test check-expensive
make[1]: Entering directory '/builds/emacs/emacs/test'
rm -f ./*.tmp
make[2]: Entering directory '/builds/emacs/emacs/test'
make[3]: Entering directory '/builds/emacs/emacs/test'
ELC lisp/net/tramp-tests.elc
GEN lisp/net/tramp-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h0m0s seconds