effects/zoom: Fix repainting with zoom factor of 1
When zoom factor is 1, the zoom effect will paint the scene in an offscreen texture, but not actually paint the textures on the screen.
Zoom factor can be 1 when the effect has been just stopped.
When zoom factor is 1, the zoom effect will paint the scene in an offscreen texture, but not actually paint the textures on the screen.
Zoom factor can be 1 when the effect has been just stopped.