I tested the fix and it successfully resolved my Warning: Attempt to read property "schemapath" on null issue

Thank you @boldc for testing. Could you also mark your successful test in Joomla Issue Tracker? That would be great, as we need two human tests as one precondition to merge a PR.

I have tested this item ✅ successfully on 5e17b7f

changing line 179 of DatabaseModel.php with the recommended code resolved this issue for me

@laoneo - I can't replicate the BEFORE condition. I installed DP Calendar 10.7.0 and no warning - not even a listing on the page /administrator/index.php?option=com_installer&view=database, so I uninstalled that and thought maybe I need to use an older version, so I installed v10.3.2 and still no warning BUT there was a line on the /administrator/index.php?option=com_installer&view=database page:

DPCalendar Component to organize events. | Administrator | Component | No Problems | 10.3.0 | ‎10.3.2 | N/A | 277

Sorry, couldn't replicate the BEFORE condition.

Joomla 5.4.4 Nightly, PHP 8.5.3

I consequently tried updating from 10.3.2 to 10.7.0 where it said I needed to upgrade to 10.6.0, which I did, then updated to 10.7.0 when I did that, the line in /administrator/index.php?option=com_installer&view=database page disappeared again.

Die you set error reporting to maximum in your Joomla configuration?

Hi @laoneo, OK, so I re-tested with Error Reporting on Maximum. With v10.3.2, no warning messages. I then installed 10.6.0 still no warning messages, then I upgraded to 10.7.0 and now I get 2 warning messages:

Warning: Attempt to read property "schemapath" on null in /home/lights/public_html/_j543/administrator/components/com_installer/src/Model/DatabaseModel.php on line 180

Warning: Trying to access array offset on null in /home/lights/public_html/_j543/administrator/components/com_installer/src/Model/DatabaseModel.php on line 180

and when I go to the Joomla Patch Tester, I also get:

Deprecated: ArrayIterator::__construct(): Using an object as a backing array for ArrayIterator is deprecated, as it allows violating class constraints and invariants in /home/lights/public_html/_j543/libraries/vendor/joomla/registry/src/Registry.php on line 256

which I understand is unrelated ).

Applying the Patch, makes BOTH messages at /administrator/index.php?option=com_installer&view=database disappear :)

As long as it is OK that there is a 2nd warning message and that it disappears, I can validate the test successful.

The patch tester issue is not related to this fix. So you can mark the test as successful. For the future, I would always test with error reporting maximum.

Deprecated: ArrayIterator::__construct(): Using an object as a backing array for ArrayIterator is deprecated, as it allows violating class constraints and invariants in /home/lights/public_html/_j543/libraries/vendor/joomla/registry/src/Registry.php on line 256

An Patch Tester issue has already been created for this at joomla-extensions/patchtester#393

I have tested this item ✅ successfully on 5e17b7f

I was able to successfully thanks @laoneo for the help.

RTC

✅ Final test before merge using JBT

• Seen the two warnings before
  • Note: it was needed to install DPCalendar-Free version 10.6.0 first and 10.7.0 second
• Applied PR with Patch Tester
  • No more warnings in Maintenance:Database
  • Tested that the database update still works with the PR
    • Created simplest component, installed sqltest-1.0.zip and checked table is created with 2 columns
    • Updated with sqltest-1.1.zip and checked third column is added

Thank you @laoneo for your contribution. Thank you @boldc and @exlemor for testing.