patch 9.0.1822: Vim9: no check for duplicate members in extended classes

Problem:  Vim9: no check for duplicate members in extended classes
Solution: Check for duplicate members in extended classes.
          Fix memory leak.

closes: #12948

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/version.c b/src/version.c
index 8f978f9..9db8a01 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1822,
+/**/
     1821,
 /**/
     1820,