Following module load exception occurs in site. DNN version - 5.1.1

DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.UI.Containers.ActionBase.get_ModuleContext() in D:\Library\UI\Containers\ActionBase.vb:line 104 at DotNetNuke.UI.Containers.ActionBase.get_ActionRoot() in D:\Library\UI\Containers\ActionBase.vb:line 87 at DotNetNuke.UI.Containers.ActionBase.Page_Load(Object sender, EventArgs e) in D:\Library\UI\Containers\ActionBase.vb:line 186 --- End of inner exception stack trace -