WindowClone: Fix some warnings on allocate

[leolost2605]

• outer_rect.width can be 0 in which case the clone_scale_factor is nan which leads to us allocating a size of nan. Therefore set the scale to 1 if the width is 0.
• clone isn't a child of us so don't allocate it
• bound the window title max width by its min width. The calculated max width could even be less than 0 which lead to allocating a negative size.

[lenemter]

LGTM