Potentially resolves https://github.com/godotengine/godot/issues/101375
VisualShader now has a has_node_embeds function that runs through it's child nodes to find embedded resources via object properties. Conversion plugin uses this function to catch the error.
Material Conversion Plugins now ERR_FAIL if called on an unitialized material.
FileSystemDock no longer crashes if Conversion Plugin fails and returns a null ref.