Hooks: Fix pointer over-advance in resort_active_iterations()

When a callback removes itself during execution and is the only entry at that priority, the internal array pointer is re-positioned by resort_active_iterations().

Before this fix, the pointer ended up at the next priority, but the subsequent next() call in the main apply_filters() loop would then advance it once more, skipping the next priority entirely.

Calling prev() ensures the pointer is balanced so the next() call lands correctly on the intended priority.

Fixes #64653.

Author: liaisontw

src/wp-includes/class-wp-hook.php

@@ -150,6 +150,11 @@ private function resort_active_iterations( $new_priority = false, $priority_exis
 				}
 			}
 
+			//If the current priority was removed, step back so the next() call in the main loop lands correctly.
+			if ( false !== current( $iteration ) && current( $iteration ) !== $current ) {
+				prev( $iteration );
+			}
+
 			// If we have a new priority that didn't exist, but ::apply_filters() or ::do_action() thinks it's the current priority...
 			if ( $new_priority === $this->current_priority[ $index ] && ! $priority_existed ) {
 				/*