From 694d04ed89f0bc1e7858cd589065bd8581010f4e Mon Sep 17 00:00:00 2001
From: grigoriliev <grigor@grigoriliev.com>
Date: Tue, 6 Dec 2016 09:53:19 +0200
Subject: [PATCH] fixed IllegalArgumentException on undo

---
 .../org/fxmisc/richtext/model/TextChange.java    | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/richtextfx/src/main/java/org/fxmisc/richtext/model/TextChange.java b/richtextfx/src/main/java/org/fxmisc/richtext/model/TextChange.java
index 04c00ef8f..61a2ae273 100644
--- a/richtextfx/src/main/java/org/fxmisc/richtext/model/TextChange.java
+++ b/richtextfx/src/main/java/org/fxmisc/richtext/model/TextChange.java
@@ -42,6 +42,22 @@ public TextChange(int position, S removed, S inserted) {
      * {@code null} otherwise.
      */
     public Optional<Self> mergeWith(Self latter) {
+        if(this.insertedLength() > 0 && this.removedLength() > 0) {
+            return Optional.empty();
+        }
+
+        if(latter.insertedLength() > 0 && latter.removedLength() > 0) {
+            return Optional.empty();
+        }
+
+        if(this.insertedLength() > 0 && latter.removedLength() > 0) {
+            return Optional.empty();
+        }
+
+        if(this.removedLength() > 0 && latter.insertedLength() > 0) {
+            return Optional.empty();
+        }
+
         if(latter.position == this.position + this.insertedLength()) {
             S removedText = concat(this.removed, latter.removed);
             S addedText = concat(this.inserted, latter.inserted);