Make fileloop skip missing files

* lisp/fileloop.el (fileloop-next-file): If a file doesn't exist,
skip to the next one (bug#44979).
3 jobs for master in 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Fast
failed #24426
test-fast-inotify

00:00:34

 
  Normal
failed #24427
test-lisp-inotify

00:00:20

failed #24428
test-lisp-net-inotify

00:00:19

 
Name Stage Failure
failed
test-lisp-net-inotify Normal There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] df1dbaf121703aebae83d2725b7aed8b961f2913 -> refs/pipelines/11654
ce8d5c6..df1dbaf master -> origin/master
Checking out df1dbaf1 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-2-build-4" is already in use by container "da1fe579c662349f5b0cbedeaf385ca8567e208eca419e08e6d3defd24c4f2dc". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-lisp-inotify Normal There has been a runner system failure, please try again
Using docker image sha256:81f5749c9058a7284e6acd8e126f2b882765a17b9ead14422b51cde1a110b85c for docker:19.03.12 ...
Running on runner-2oEDrUT7-project-1-concurrent-1 via emba.gnu.org...
$ git config --global http.proxy $HTTP_PROXY; git config --global https.proxy $HTTPS_PROXY
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
Checking out df1dbaf1 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)
failed
test-fast-inotify Fast There has been a runner system failure, please try again
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/emacs/emacs/.git/
From https://emba.gnu.org/emacs/emacs
* [new ref] df1dbaf121703aebae83d2725b7aed8b961f2913 -> refs/pipelines/11654
ce8d5c6..df1dbaf master -> origin/master
Checking out df1dbaf1 as master...

Skipping Git submodules setup
ERROR: Job failed (system failure): Error response from daemon: Conflict. The container name "/runner-2oEDrUT7-project-1-concurrent-1-build-4" is already in use by container "f46df44a43bee1f61a6ede2eac732a4e06eaa2094659f7ea23718f093d67bcc6". You have to remove (or rename) that container to be able to reuse that name. (executor_docker.go:726:0s)