patch 9.1.0601: Wrong cursor position with 'breakindent' when wide char doesn't fit

Problem:  Wrong cursor position with 'breakindent' when a double-width
          character doesn't fit in a screen line (mikoto2000)
Solution: Include the width of the 'breakindent' properly.
          (zeertzjq)

fixes: #15289
closes: #15290

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/charset.c b/src/charset.c
index 45b16aa..19b0895 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1397,17 +1397,17 @@
 		else if (max_head_vcol > vcol + head_prev + prev_rem)
 		    head += (max_head_vcol - (vcol + head_prev + prev_rem)
 					     + width2 - 1) / width2 * head_mid;
-#  ifdef FEAT_PROP_POPUP
 		else if (max_head_vcol < 0)
 		{
-		    int off = 0;
+		    int off = mb_added;
+#  ifdef FEAT_PROP_POPUP
 		    if (*s != NUL
 			     && ((State & MODE_NORMAL) || cts->cts_start_incl))
 			off += cts->cts_cur_text_width;
+#  endif
 		    if (off >= prev_rem)
 			head += (1 + (off - prev_rem) / width) * head_mid;
 		}
-#  endif
 	    }
 	}