evas gl: init evgl during eng_gl_get_pixels_pre()

when the first render is an image without a native surface,
evgl_init() will not be called before this point, resulting in an abort()

src/modules/evas/engines/gl_generic/evas_engine.c

@@ -1660,8 +1660,9 @@ eng_gl_get_pixels_set(void *data, void *get_pixels, void *get_pixels_data, void
 }
 
 static void
-eng_gl_get_pixels_pre(void *data EINA_UNUSED)
+eng_gl_get_pixels_pre(void *data)
 {
+   EVGLINIT(data, );
    evgl_get_pixels_pre();
 }