patch 8.2.1946: sort() with NULL string not tested

Problem:    sort() with NULL string not tested.
Solution:   Add a test.  use v:collate. (Dominique Pellé, closes #7247)
diff --git a/src/version.c b/src/version.c
index 8052de8..3f2affe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1946,
+/**/
     1945,
 /**/
     1944,