patch 9.0.2091: Vim9: cannot convert list to string using +=

Problem:  Vim9: cannot convert list to string using +=
          (after 9.0.2072)
Solution: convert dict index to string later in compile_member()

fixes: #13485
closes: #13486

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index cd512da..3a72a9c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2091,
+/**/
     2090,
 /**/
     2089,