From d662f5aa63b205cc20f34e2c597ac8a2e1fc0bf3 Mon Sep 17 00:00:00 2001
From: Juan Linietsky <reduzio@gmail.com>
Date: Tue, 14 Jun 2016 08:48:34 -0300
Subject: [PATCH] does not fix the bug reported in #4326 and #4818, but at
 least make sure it throws and error and does not crash

(cherry picked from commit 333de40180d7d8d6890cceaa1bc3d46efa2b5083)
---
 scene/gui/text_edit.cpp | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/scene/gui/text_edit.cpp b/scene/gui/text_edit.cpp
index d1c4374f8e4..0e8e0d60b21 100644
--- a/scene/gui/text_edit.cpp
+++ b/scene/gui/text_edit.cpp
@@ -3736,12 +3736,16 @@ void TextEdit::undo() {
 	_do_text_op(op, true);
 	current_op.version=op.prev_version;
 	if(undo_stack_pos->get().chain_backward) {
-		do {
+		while(true) {
+			ERR_BREAK(!undo_stack_pos->prev());
 			undo_stack_pos = undo_stack_pos->prev();
 			op = undo_stack_pos->get();
 			_do_text_op(op, true);
 			current_op.version = op.prev_version;
-		} while(!undo_stack_pos->get().chain_forward);
+			if (undo_stack_pos->get().chain_forward) {
+				break;
+			}
+		}
 	}
 
 	cursor_set_line(undo_stack_pos->get().from_line);
@@ -3760,12 +3764,16 @@ void TextEdit::redo() {
 	_do_text_op(op, false);
 	current_op.version = op.version;
 	if(undo_stack_pos->get().chain_forward) {
-		do {
+
+		while(true) {
+			ERR_BREAK(!undo_stack_pos->next());
 			undo_stack_pos=undo_stack_pos->next();
 			op = undo_stack_pos->get();
 			_do_text_op(op, false);
 			current_op.version = op.version;
-		} while(!undo_stack_pos->get().chain_backward);
+			if (undo_stack_pos->get().chain_backward)
+				break;
+		}
 	}
 	cursor_set_line(undo_stack_pos->get().to_line);
 	cursor_set_column(undo_stack_pos->get().to_column);