patch 8.2.2984: Vim9: test fails because of missing return statement

Problem:    Vim9: Test fails because of missing return statement.
Solution:   When type is unknown set type to void.
diff --git a/src/version.c b/src/version.c
index fcb0d92..7f459c2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2984,
+/**/
     2983,
 /**/
     2982,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index dfd5aaa..47847af 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -9596,7 +9596,9 @@
 
     if (!cctx.ctx_had_return)
     {
-	if (ufunc->uf_ret_type->tt_type != VAR_VOID)
+	if (ufunc->uf_ret_type->tt_type == VAR_UNKNOWN)
+	    ufunc->uf_ret_type = &t_void;
+	else if (ufunc->uf_ret_type->tt_type != VAR_VOID)
 	{
 	    emsg(_(e_missing_return_statement));
 	    goto erret;