patch 8.2.4642: Vim9: in :def function script var cannot be null
Problem: Vim9: in :def function script var cannot be null.
Solution: Only initialize a script variable when not set to a null value.
(closes #10034)
diff --git a/src/vim.h b/src/vim.h
index 13ce032..d9bd51b 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2229,6 +2229,7 @@
#define ASSIGN_UNPACK 0x10 // using [a, b] = list
#define ASSIGN_NO_MEMBER_TYPE 0x20 // use "any" for list and dict member type
#define ASSIGN_FOR_LOOP 0x40 // assigning to loop variable
+#define ASSIGN_INIT 0x80 // not assigning a value, just a declaration
#include "ex_cmds.h" // Ex command defines
#include "spell.h" // spell checking stuff