elementary: Check for valid resize object before calling

Summary:
efl_layout_signal_emit

This patch fixes an issue where NULL was passed to
efl_layout_signal_emit due to wd->resize_obj being NULL. This was
discovered in Enlightenment by clicking on the mixer module and trying
to close the popup window

ref T7030
Depends on D6638

Reviewers: zmike

Reviewed By: zmike

Subscribers: Hermet, cedric, committers

Tags: efl

Maniphest Tasks: T7030

Differential Revision: https://phab.enlightenment.org/D6639