Double Fxaa deserialize error

The deserialization process reports an error when two Fxaa scenarios exist.

The Fxaa’s width and height were assigned values during deserialization, and the loadTexture of the second Fxaa was not loaded successfully due to the assignment, which caused the scene rendering to fail. The deserialization process of Fxaa should not assign values to width and height.

This PR will fix the problem: