patch 8.2.4586: Vim9: no error for using lower case name for "func" argument

Problem:    Vim9: no error for using lower case name for "func" argument.
            (Ernie Rael)
Solution:   Check the name as soon as the type is known.
diff --git a/src/userfunc.c b/src/userfunc.c
index 6a5d84b..ce2ad13 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -429,6 +429,12 @@
 		if (type == NULL)
 		    return FAIL;
 		fp->uf_arg_types[i] = type;
+		if (i < fp->uf_args.ga_len
+			&& (type->tt_type == VAR_FUNC
+			    || type->tt_type == VAR_PARTIAL)
+			&& var_wrong_func_name(
+				    ((char_u **)fp->uf_args.ga_data)[i], TRUE))
+		    return FAIL;
 	    }
 	}
     }