patch 9.0.1944: Vim9: function instruction pointer invalidated

Problem:  Vim9: function instruction pointer invalidated
Solution: Use the funcref index instead of the instruction pointer

closes: #13178
closes: #13196

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/proto/vim9instr.pro b/src/proto/vim9instr.pro
index aef934f..44e6b98 100644
--- a/src/proto/vim9instr.pro
+++ b/src/proto/vim9instr.pro
@@ -45,7 +45,7 @@
 int generate_VIM9SCRIPT(cctx_T *cctx, isntype_T isn_type, int sid, int idx, type_T *type);
 int generate_NEWLIST(cctx_T *cctx, int count, int use_null);
 int generate_NEWDICT(cctx_T *cctx, int count, int use_null);
-int generate_FUNCREF(cctx_T *cctx, ufunc_T *ufunc, class_T *cl, int fi, isn_T **isnp);
+int generate_FUNCREF(cctx_T *cctx, ufunc_T *ufunc, class_T *cl, int fi, int *isn_idx);
 int generate_NEWFUNC(cctx_T *cctx, char_u *lambda_name, char_u *func_name);
 int generate_DEF(cctx_T *cctx, char_u *name, size_t len);
 int generate_JUMP(cctx_T *cctx, jumpwhen_T when, int where);