Fix: An unprintable multi-byte character at the start of the screen line

caused the following text to be drawn at the wrong position.

runtime/doc/todo.txt

@@ -33,9 +33,6 @@ be worked on, but only if you sponsor Vim development.  See |sponsor|.
 Before release 7.3:
 - Rename vim73 branch to default (hints: Xavier de Gaye, 2010 May 23)
 
-Better Czech keymap. (Stepnem, 2010 May 4)  Use if no response from Jiri
-Tobisek.
-
 :!cmd completion doesn't work on Windows. (Yue Wu).
 Problem with space in path?
 

src/screen.c

@@ -4005,8 +4005,9 @@ win_line(wp, lnum, startrow, endrow, nochange)
 		    ptr += mb_l - 1;
 
 		/* If a double-width char doesn't fit at the left side display
-		 * a '<' in the first column. */
-		if (n_skip > 0 && mb_l > 1)
+		 * a '<' in the first column.  Don't do this for unprintable
+		 * charactes. */
+		if (n_skip > 0 && mb_l > 1 && n_extra == 0)
 		{
 		    n_extra = 1;
 		    c_extra = '<';