patch 8.2.3100: Vim9: no error when using type with unknown number of args

Problem:    Vim9: no error when using type with unknown number of arguments.
Solution:   Do not ignore argument count of -1. (closes #8492)
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 86f890e..92ffa00 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -650,6 +650,15 @@
     d.dd[0] = 0
   END
   CheckDefExecFailure(lines, 'E1147:', 2)
+
+  lines =<< trim END
+      def OneArg(x: bool)
+      enddef
+      def TwoArgs(x: bool, y: bool)
+      enddef
+      var fl: list<func(bool, bool, bool)> = [OneArg, TwoArgs]
+  END
+  CheckDefExecAndScriptFailure(lines, 'E1012:', 5)
 enddef
 
 def Test_assignment_list_any_index()