ecore_evas_extn: Modify not to send a message if there is nothing to draw

ecore_evas_extn: Modify not to send a message if there is nothing to draw

Summary:
Seding ipc messages on ews_update_image(which is invoked as a callback of EVAS_RENDER_POST)
can makes ecore main loop awake, because sending ipc messages makes message_queue not empty.

so that this patch prevent seding ipc logic if there is nothing to draw.

Reviewers: cedric, raster

Reviewed By: raster

Subscribers: zmike

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D6055

Change-Id: Ibd11e40c5d1edaf2e94a8a00ae309d05c61c4ea1