EvasGL: Add error handling for GL_OES_EGL_image/EGL_Image_KHR

EvasGL: Add error handling for GL_OES_EGL_image/EGL_Image_KHR

Summary:
Add code for exception case for GL_OES_EGL_image/EGL_Image_KHR
These EvasGL's extension functions does not have the code for exception case.
e.g. EvasGLImage is NULL.

Test Plan: Native Pixmap surface's example is created and changed EvasGLImage's value(e.g. valid data or NULL)

Reviewers: raster, spacegrapher, jpeg

Subscribers: scholb.kim, JoogabYun, dkdk, cedric

Differential Revision: https://phab.enlightenment.org/D3284

From 64890d260f9ee9607aa21e52761bba226a7b0bd1 Mon Sep 17 00:00:00 2001
From: Wonsik Jung <sidein@samsung.com>

Change-Id: Idb8eebbca8c6f02ea9fe66ad2a3ec455f085409d