Fix blender environment map texture looking different on the first render with

an image file, the image extend is set automatically when render starts but not
when the image was never loaded yet.

source/blender/render/intern/source/envmap.c

@@ -722,6 +722,10 @@ int envmaptex(Tex *tex, const float texvec[3], float dxt[3], float dyt[3], int o
 					envmap_split_ima(env, ibuf_ima);
 				else
 					env->ok = 0;
+
+				if (env->type == ENV_PLANE)
+					tex->extend = TEX_EXTEND;
+
 				BKE_image_pool_release_ibuf(env->ima, ibuf_ima, pool);
 			}
 		}