Applied asp cookie patch submitted by Jan van der Lugt

aspclassiccompiler/asp/BuiltInObjects/AspCookieCollection.cs

@@ -46,6 +46,9 @@ namespace Dlrsoft.Asp.BuiltInObjects
                 else
                     cookie = _cookiecollection[(string)key];
 
+                if (cookie == null)
+                    return "";
+
                 if (_request)
                     return new AspReadCookie(cookie);
                 else

aspclassiccompiler/asp/BuiltInObjects/AspReadCookie.cs

@@ -50,7 +50,7 @@ namespace Dlrsoft.Asp
 
         public override string ToString()
         {
-            if (_cookie == null) return null;
+            if (_cookie == null) return "";
 
             StringBuilder sb = new StringBuilder();
             bool first = true;