patch 9.1.0172: More code can use ml_get_buf_len() instead of STRLEN()

Problem:  More code can use ml_get_buf_len() instead of STRLEN().
Solution: Change more STRLEN() calls to ml_get_buf_len().  Also do not
          set ml_line_textlen in ml_replace_len() if "has_props" is set,
          because "len_arg" also includes the size of text properties in
          that case. (zeertzjq)

closes: #14183

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/channel.c b/src/channel.c
index 8d850c6..b99b3a9 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -1493,7 +1493,7 @@
 write_buf_line(buf_T *buf, linenr_T lnum, channel_T *channel)
 {
     char_u  *line = ml_get_buf(buf, lnum, FALSE);
-    int	    len = (int)STRLEN(line);
+    int	    len = ml_get_buf_len(buf, lnum);
     char_u  *p;
     int	    i;