PHP error on replace_editor filter

Hi there

In \ProDevign\BlockMeister\Context::is_block_editor there is a check on whether we are currently on the block editor. The first check does the following:
– Gather the global $post.
– Use it to gather the result of the replace_editor filter.

This method is used wildly along the plugin, even on pages where the global $post is not set. However, as stated in the docs, that $post parameter must indeed be a WP_Post instance.

A plugin of ours adds a callback to that replace_editor filter, and of course, expects that its second parameter is a proper WP_Post instance. As a result, we get a PHP error when both ours and your plugin are active.

I would suggest checking that the global $POST is indeed a WP_Post object before running it over the filter, and avoiding using the filter as a source of truth if that check fails.