fix(files): Do not fail on missing sidebar in files list

[eszkadev]

When using richdocuments it was failing in case of shared links or when user with opened file did a wheel click on a refresh page. Then new tab appeared but instead opening the file it was doing nothing (showing the list of files) or downloading the file.

Make code more defensive. I found these logs while debugging:

OCA.Files.Settings initialized
Sidebar.js:19 OCA.Files.Sidebar initialized
ShareSearch.js:16 OCA.Sharing.ShareSearch initialized comments-app.js:15 OCA.Comments.View initialized
index.mjs:54 [ERROR] files: Error while opening sidebar Object log @ index.mjs:54
index.mjs:54 [ERROR] files: Error while opening sidebar Objectapp: "files"error: TypeError: window.OCA.Files.Sidebar.open is not a function
    at h.exec (http://nc/dist/files-main.js?v=106d16db-0:1:70123)
    at o.openSidebarForFile (http://nc/dist/files-main.js?v=106d16db-0:1:163422)
    at o.handleOpenQueries (http://nc/dist/files-main.js?v=106d16db-0:1:163167)
    at o.openDetails (http://nc/dist/files-main.js?v=106d16db-0:1:162349)
    at fn (http://nc/dist/core-common.js?v=106d16db-0:1:3942538)
    at e.run (http://nc/dist/core-common.js?v=106d16db-0:1:3946900)
    at sa (http://nc/dist/core-common.js?v=106d16db-0:1:3948728)
    at Array.<anonymous> (http://nc/dist/core-common.js?v=106d16db-0:1:3943585)
    at bn (http://nc/dist/core-common.js?v=106d16db-0:1:3942986)level: 2uid: "admin"[[Prototype]]: Object
log @ index.mjs:54

Possibly regression from
e700102

Fixes nextcloud/richdocuments#3815

[juliusknorr]

/compile

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[skjnldsv]

/compile rebase

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

[skjnldsv]

/backport dc3741a to stable32

[skjnldsv]

/backport dc3741a to stable31

[eszkadev]

thank you very much for solving conflicts :)