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When download a public link share folder using the button on the top
right, it doesn't provide a list of files.

This fix makes sure to trigger the correct logic when no file list was
given.

Probably nice for the people that contributed to 9.0 to see themselves in the AUTHORS file :)

* Made comments more clear
* Removed unneeded methods
* IShares shareTime is now a proper DateTime object
* IShares getPath -> getNode & setPath -> setNode
* Fix unit tests

* Updated unit tests

Nice side effect... pure unit tests!

This commit consists of patches automatically generated for this project on https://scrutinizer-ci.com

Currently the `getPath` methods returned `NULL` in case when a file with the specified ID does not exist. This however mandates that developers are checking for the `NULL` case and if they do not the door for bugs with all kind of impact is widely opened.

This is especially harmful if used in context with Views where the final result is limited based on the result of `getPath`, if `getPath` returns `NULL` PHP type juggles this to an empty string resulting in all possible kind of bugs.

While one could argue that this is a misusage of the API the fact is that it is very often misused and an exception will trigger an immediate stop of execution as well as log this behaviour and show a pretty error page.

I also adjusted some usages where I believe that we need to catch these errors, in most cases this is though simply an error that should hard-fail.

The sharing backend may throw another exception for example when the activity app encounters a problem. Previously this just triggered a 404 error page and the exception got not logged at all. With this change such exceptions get not intercepted and regularly handled as exceptions so that we have meaningful log data. Also the user will be shown a window informing him that an error happened.

Helps to debug cases such as https://github.com/owncloud/core/issues/19465

This commit consists of patches automatically generated for this project on https://scrutinizer-ci.com

 *cough* *cough*

Despite it's PHPDoc the function might return `null` which was not properly catched and thus in some situations the share was resolved to the sharing users root directory.

To test this perform the following steps:

* Share file in owncloud 7 (7.0.4.2)
* Delete the parent folder of the shared file
* The share stays is in the DB and the share via the sharelink is inaccessible. (which is good)
* Upgrade to owncloud 8 (8.0.2) (This step is crucial. The bug is not reproduceable without upgrading from 7 to 8. It seems like the old tokens are handled different than the newer ones)
* Optional Step: Logout, Reset Browser Session, etc.
* Access the share via the old share url: almost empty page, but there is a dowload button which adds a "/download" to the URL.
* Upon clicking, a download.zip is downloaded which contains EVERYTHING from the owncloud directory (of the user who shared the file)
* No exception is thrown and no error is logged.

This will add a check whether the share is a valid one and also adds unit tests to prevent further regressions in the future. Needs to be backported to ownCloud 8.

Adding a proper clean-up of the orphaned shares is out-of-scope and would probably require some kind of FK or so.

Fixes https://github.com/owncloud/core/issues/15097