bdiff: one more safe call of bdiff_freehunks(NULL)

bdiff: one more safe call of bdiff_freehunks(NULL)

--- a/mercurial/cext/bdiff.c	Thu Jun 14 20:25:16 2018 +0900
+++ b/mercurial/cext/bdiff.c	Thu Jun 14 20:25:51 2018 +0900
@@ -157,9 +157,7 @@
 	PyBuffer_Release(&bb);
 	free(al);
 	free(bl);
-	if (l.next) {
-		bdiff_freehunks(l.next);
-	}
+	bdiff_freehunks(l.next);
 	return result;
 }