scene: Pad damage if scale factor is fractional
Floating point arithmetic and/or the use of GL_LINEAR in the pipeline, may result in visual glitches due to rounding (errors). As a short-term fix until a proper (more involved) solution is in place for Plasma 6, pad the damage slightly in all directions to alleviate those effects.
(cherry picked from commit 56f6bab0)
To be merged after a week of testing of 56f6bab0