Fix #29764: Crash when border rendering in sequencer. (Not Cycles related)

Sequencer render context should be as large as the whole frame when rendering
using border without clipping.

Can be implemented in more clear way but it'll require more global refactoring.

source/blender/render/intern/source/pipeline.c

@@ -2538,9 +2538,17 @@ static void do_render_seq(Render * re)
 
 	recurs_depth++;
 
-	context = seq_new_render_data(re->main, re->scene,
-				      re->result->rectx, re->result->recty, 
-				      100);
+	if((re->r.mode & R_BORDER) && (re->r.mode & R_CROP)==0) {
+		/* if border rendering is used and cropping is disabled, final buffer should
+		    be as large as the whole frame */
+		context = seq_new_render_data(re->main, re->scene,
+					      re->winx, re->winy,
+					      100);
+	} else {
+		context = seq_new_render_data(re->main, re->scene,
+					      re->result->rectx, re->result->recty,
+					      100);
+	}
 
 	ibuf = give_ibuf_seq(context, cfra, 0);