After 4 sites were successfully upgraded from 5.1 to 5.6, I tried another site. Now, that site is getting errors!

The first error was:
file: App_Code\Chat\DnnChatCodeHelper.vb

line 309: Dim ctx As Web.HttpContext = Web.HttpContext.Current

error: Type 'Web.HttpContext' is not defined.


I got by that by simply removing the Chat directory.

Now, I'm getting another error:

Object reference not set to an instance of an object.

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Tabs.TabController.GetTabByTabPath(Int32 portalId, String tabPath) +15
   DotNetNuke.HttpModules.UrlRewriteModule.RewriteUrl(HttpApplication app) +3600
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +1291
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +68
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

Hello, I am having the second error after trying to update to 5.06.03 from 5.2.1. I rolled back to the backup after errors, and now get that error. I have tried your suggestion to no avail. Thanks in advance for your help.

Server Error in '/' Application.
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Object reference not set to an instance of an object.
  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

 Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

 An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. 

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Tabs.TabController.GetTabByTabPath(Int32 portalId, String tabPath) +15
   DotNetNuke.HttpModules.UrlRewriteModule.RewriteUrl(HttpApplication app) +3600
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +1291
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +68
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

 

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Version Information: Microsoft .NET Framework