Make sure the view exists before adding it to the menu lookup array, remove PHP Notices

[csthomas]

Other solution for the same problem as in #17323, #18043

Summary of Changes

Do not add view name to the menu lookup array if the view does not exists.

Remove PHP Notice:
Notice: Undefined index: loginx in .../libraries/src/Component/Router/Rules/MenuRules.php on line 216

Notice: Trying to get property of non-object in .../libraries/src/Component/Router/Rules/MenuRules.php on line 216

Testing Instructions

1. Install joomla.

2. Go to backend and edit a menu item.

3. Change name of view in the link field and save.
   Please see attached video. I used FF Inspector (Ctrl + Shift + C)
   

4. Go to frontend in order to see changes.

5. Before PR there are 2 php notices, after PR they disappear.

Expected result

No PHP Notices

Actual result

PHP Notices.

Documentation Changes Required

No

[csthomas]

Anyone who has tested this PR can login at https://issues.joomla.org/tracker/joomla-cms/18564 and mark the test as successful.

[ciar4n]

I have tested this item ✅ successfully on 16c361c

Both PHP errors gone with PR.

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[Quy]

In your video, after clicking the Save button, the Menu Item Type is blank. Is that right?

[csthomas]

Yes, view loginx has never exist.
View section existed in older joomla version but you will get the same result, blank menu type.

I do not have other idea how to test old menu item that currently does not exists.

This is only a example (a way) to create a menu item that for now does not exist, like with view section.

After you create invalid menu item, means with view that is invalid then you get php notices - on front end - before PR.

[fancyFranci]

I have tested this item ✅ successfully on 16c361c

Tested like in the instructions. Nice gif btw!

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[ghost]

RTC after two successful tests.