Fix toString of ConfigDelayedMerge, the default render() in superclas…

…s didn't work

The superclass called unwrapped() to render, which isn't allowed here.

config/src/main/java/com/typesafe/config/impl/ConfigDelayedMerge.java

@@ -270,6 +270,11 @@ protected void render(StringBuilder sb, int indent, boolean atRoot, String atKey
         render(stack, sb, indent, atRoot, atKey, options);
     }
 
+    @Override
+    protected void render(StringBuilder sb, int indent, boolean atRoot, ConfigRenderOptions options) {
+        render(sb, indent, atRoot, null, options);
+    }
+
     // static method also used by ConfigDelayedMergeObject.
     static void render(List<AbstractConfigValue> stack, StringBuilder sb, int indent, boolean atRoot, String atKey,
             ConfigRenderOptions options) {