Viewport does not properly maintain size when FilterPostProcessor is added to it

[ASneakyFox]

This issue primarily manifests itself when trying to add a second viewport that acts as "pip viewport" rather than one that takes up the full screen

When a viewport is resized to act as a pip viewport it normally works fine. however once adding the FilerPostProcessor to it, it will then lose it's dimensions and behave in a weird and undesired way.

a full description/discussion of this problem is here: http://hub.jmonkeyengine.org/forum/topic/viewport-sizing-and-the-filterpostprocessor/

test case that will reproduce the bug: http://pastebin.com/p4kHZrSQ

[stephengold]

I'm having difficulty reproducing this issue using the pastebin test case and current master branch. I don't see anything weird. Commenting out the bloom filter has no effect on the viewport layout.

I suspect this issue might have been related to issue #357, which was fixed in 2017.