Fixed debugging printing when type printing delegate is not initialized.

Author: tritao

src/AST/Type.cs

@@ -30,7 +30,7 @@ public abstract T Visit<T>(ITypeVisitor<T> visitor, TypeQualifiers quals
 
         public override string ToString()
         {
-            return TypePrinterDelegate(this);
+            return TypePrinterDelegate == null ? base.ToString() : TypePrinterDelegate(this);
         }
 
         public abstract object Clone();