fix restore size when float is used

it was technically possible for geometries to not be integer, but
a string to int parse was done, so teoretically string.toInt() can
fail and reset position/size of the plasmoid.
It may be the cause of some of the positions lost bugs.
This was particularly evident and triggerable in plasma mobile.
on palsma mobile side was also fixed by making suire the grid size is
always int, however technically the bug is here too as well