Code review comment for lp://staging/~raof/qtmir/multi-bufferstream-support

I updated the branch [1] with more fixes.

5) Fixed the node leak.

6) Switched back to stretched fill mode. I had to rework the loop a bit so that the geometry size is updated when the item size changes.

Feel free to merge that if you think it's fine.

[1] https://code.launchpad.net/~loic.molinari/qtmir/multi-bufferstream-support-fixes