patch 9.1.0140: cursor on wrong row after 1 char 'below' virtual text when EOL is shown

Problem:  The cursor screen row was incorrectly being calculated when the
          cursor follows a 1 character text_align 'below' virtual text line,
          resulting in the cursor being shown on the wrong line.
          This was caused by a cell size of 2 instead of 1 being used for the EOL
          character, which propagated to the calculation of space for putting the
          'below' virtual text on its own line. (rickhowe)
Solution: Fix the size used for the EOL character in calculating the
          cursor's screen position (Dylan Thacker-Smith)

fixes: #11959
related: #12028
closes: #14096

Signed-off-by: Dylan Thacker-Smith <dylan.ah.smith@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/charset.c b/src/charset.c
index 919885d..9f4c0ae 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1160,8 +1160,12 @@
      * First get the normal size, without 'linebreak' or text properties
      */
     size = win_chartabsize(wp, s, vcol);
-    if (*s == NUL && !has_lcs_eol)
-	size = 0;  // NUL is not displayed
+    if (*s == NUL)
+    {
+	// 1 cell for EOL list char (if present), as opposed to the two cell ^@
+	// for a NUL character in the text.
+	size = has_lcs_eol ? 1 : 0;
+    }
 # ifdef FEAT_LINEBREAK
     int is_doublewidth = has_mbyte && size == 2 && MB_BYTE2LEN(*s) > 1;
 # endif