Fix bug with parsing improper module separator.

tests/modules.rs

@@ -14,6 +14,13 @@ fn test_module() {
     assert_eq!(module.get_var_value::<INT>("answer").unwrap(), 42);
 }
 
+#[test]
+fn test_module_syntax() {
+    let engine = Engine::new();
+    assert!(engine.compile("abc.def::xyz").is_err());
+    assert!(engine.compile("abc.def::xyz()").is_err());
+}
+
 #[test]
 fn test_module_sub_module() -> Result<(), Box<EvalAltResult>> {
     let mut module = Module::new();