Fix for incorrect undo after 'backspace' at column 0 (concatenating the current line to the previous line). The undo start location should be at the end of the previous line.

TextEditor.cpp

diff --git a/TextEditor.cpp b/TextEditor.cpp
index c35c2a2..bf9240e 100644
--- a/TextEditor.cpp
+++ b/TextEditor.cpp
@@ -1314,7 +1314,7 @@
 				return;

 

 			u.mRemoved = '\n';

-			u.mRemovedStart = u.mRemovedEnd = GetActualCursorCoordinates();

+			u.mRemovedStart = u.mRemovedEnd = Coordinates(pos.mLine - 1, (int)mLines[pos.mLine - 1].size());

 			Advance(u.mRemovedEnd);

 

 			auto& line = mLines[mState.mCursorPosition.mLine];