patch 8.1.0581: double free without the text properties feature

Problem:    Double free without the text properties feature.
Solution:   Reset the dirty flag.

src/memline.c

@@ -3176,9 +3176,9 @@ ml_replace_len(linenr_T lnum, char_u *line_arg, colnr_T len_arg, int copy)
     {
 	// another line is buffered, flush it
 	ml_flush_line(curbuf);
+	curbuf->b_ml.ml_flags &= ~ML_LINE_DIRTY;
 
 #ifdef FEAT_TEXT_PROP
-	curbuf->b_ml.ml_flags &= ~ML_LINE_DIRTY;
 	if (has_any_text_properties(curbuf))
 	    // Need to fetch the old line to copy over any text properties.
 	    ml_get_buf(curbuf, lnum, TRUE);

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    581,
 /**/
     580,
 /**/