patch 8.2.2782: Vim9: blob operations not fully tested

Problem:    Vim9: blob operations not fully tested.
Solution:   Make more blob tests run in Vim9 script.  Fix filter().  Make
            insert() give an error for a null blob, like add().
diff --git a/src/version.c b/src/version.c
index 6216faf..811370c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2782,
+/**/
     2781,
 /**/
     2780,