patch 9.1.0151: ml_get_buf_len() does not consider text properties

Problem:  ml_get_buf_len() does not consider text properties
          (zeertzj)
Solution: Store text length excluding text properties length
          in addition in the memline

related #14123
closes: #14133

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/change.c b/src/change.c
index 42e6f793..847c187 100644
--- a/src/change.c
+++ b/src/change.c
@@ -1364,6 +1364,7 @@
 	    mch_memmove(newp + newlen + 1, oldp + oldlen + 1,
 			       (size_t)curbuf->b_ml.ml_line_len - oldlen - 1);
 	curbuf->b_ml.ml_line_len -= count;
+	curbuf->b_ml.ml_line_textlen = (int)STRLEN(newp) + 1;
     }
 #endif