Don't throw exceptions if SemanticsOwnerListenerImpl.current is null,…

… early exit instead (#1114)

## Proposed Changes

Replace throwing `SemanticsOwnerListenerImpl.current` check with early
exit check.

## Testing

Test: N/A

## Issues Fixed

Fixes: JetBrains/compose-multiplatform#4315

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/scene/ComposeSceneMediator.uikit.kt

@@ -135,7 +135,7 @@ private class SemanticsOwnerListenerImpl(
     }
 
     override fun onSemanticsOwnerRemoved(semanticsOwner: SemanticsOwner) {
-        val current = checkNotNull(current)
+        val current = current ?: return
 
         if (current.first == semanticsOwner) {
             current.second.dispose()