Fix fatal error when activating LifterLMS (#2189)

Ref: https://wordpress.org/support/topic/lifterlms-fatal-error/

To reproduce the original issue: activate GravityView (`develop` branch)
followed by LifterLMS.

After the fix:

![CleanShot 2024-11-02 at 09 50
21@2x](https://github.com/user-attachments/assets/6c81213f-493f-4bcb-984e-f73e6ea84fa8)

I did not test the actual functionality, but all settings work.

💾 [Build
file](https://www.dropbox.com/scl/fi/s8lds3vs7lswre571jb2d/gravityview-2.31-43a55ba24.zip?rlkey=o4folrfrvntonowdozee2izme&dl=1)
(43a55ba).

includes/class-admin-welcome.php

@@ -316,6 +316,7 @@ public function changelog_screen() {
 					<li>JavaScript enqueued in the site's footer was not executed when editing an entry in the lightbox.</li>
 					<li>It was not possible to add new entry notes when viewing a single entry in the lightbox.</li>
 					<li>Validation error displayed when adding merge tags to the Entry Slug setting input in the View editor.</li>
+					<li>Fatal error when activating LifterLMS with GravityView active.</li>
 					<li>Searching across all fields not working as expected when the search value contains special characters or accents (e.g., ä, ß, İ).</li>
 				</ul>