patch 9.1.0581: Various lines are indented inconsistently

Problem:  style: Various lines are indented inconsistently
Solution: Retab these lines and correct some comments.
          (zeertzjq)

closes: #15259

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/memline.c b/src/memline.c
index 6c63fad..9e579cd 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -2710,7 +2710,7 @@
     char_u	*line;
 
     if (*(line = ml_get_buf(buf, lnum, FALSE)) == NUL)
-        return 0;
+	return 0;
 
     if (buf->b_ml.ml_line_textlen <= 0)
 	buf->b_ml.ml_line_textlen = (int)STRLEN(line) + 1;