Simplify listInstancePath_class

This is now in line with the condition in leafListElementPath_class.

Change-Id: Ic5a92c8b4e1a88215d0e197bbd67c2616811c99b
diff --git a/src/ast_handlers.hpp b/src/ast_handlers.hpp
index ca39b21..540d7e2 100644
--- a/src/ast_handlers.hpp
+++ b/src/ast_handlers.hpp
@@ -197,13 +197,7 @@
     void on_success(Iterator const&, Iterator const&, T& ast, Context const& context)
     {
         auto& parserContext = x3::get<parser_context_tag>(context);
-        if (ast.m_nodes.empty()) {
-            parserContext.m_errorMsg = "This is not a list instance.";
-            _pass(context) = false;
-            return;
-        }
-
-        if (!std::holds_alternative<listElement_>(ast.m_nodes.back().m_suffix)) {
+        if (ast.m_nodes.empty() || !std::holds_alternative<listElement_>(ast.m_nodes.back().m_suffix)) {
             parserContext.m_errorMsg = "This is not a list instance.";
             _pass(context) = false;
         }