patch 8.1.0581: double free without the text properties feature

Problem:    Double free without the text properties feature.
Solution:   Reset the dirty flag.
diff --git a/src/memline.c b/src/memline.c
index 59e4502..0eb31c3 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -3176,9 +3176,9 @@
     {
 	// 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);
diff --git a/src/version.c b/src/version.c
index 9f097af..9a44976 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    581,
+/**/
     580,
 /**/
     579,