genlist - don't do heavy queue work for 0 width genlists and defer fill

genlist - don't do heavy queue work for 0 width genlists and defer fill

Scenario:
1. Create elm_genlist.
2. Add some items to it.
3. Do not resize the genlist and leave it with width == 0.

PROPOSAL:
1. When the element is queued for recalculation check current width of
widget. If it is equal to 0 do not add idle enterer.
2. In smart callback on resize check if queue of items that need
recalculation is not empty and new width is not 0. In this situation
add idle enterer.