[php-src] Issue #10726: Cannot "unregister" a function, collation or aggregate in SQLite3 extension

Issue: https://github.com/php/php-src/issues/10726 Author: bohwaz ### Description The following code: ```php <?php $db = new SQLite3(':memory:'); $db->createFunction('like', 'strcmp'); $db->createFunction('like', null); ``` Resulted in this output: ``` Argument #2 ($callback) must be of type callable, null given ``` But I expected to be able to unregister the custom like function, as documented in SQLite doc: > To delete an existing SQL function or aggregate, pass NULL pointers for all three function > callbacks. https://www.sqlite.org/c3ref/create_function.html Passing NULL to SQLite3::create* methods should un-register the existing function. ### PHP Version Any ### Operating System _No response_