How to solve Violation of PRIMARY KEY constraint error which is coming from sp ?

{Violation of PRIMARY KEY constraint PK__#B12AD42__19093A2B4B4AF11E. Cannot insert duplicate key in object dbo.@TCategory. The duplicate key value is (0).\r\nThe statement has been terminated.}

ALTER PROCEDURE [dbo].[spGetAllProjectAndTaskForUser]
	  @EmpID INT 
	, @UserID int
	, @ProjectName NVARCHAR(MAX)
	, @Status XML
	, @Category XML
	, @Priority XML
	, @Location XML	
	, @IsAdvanceSearch BIT = NULL
	, @StartDate DateTime
	, @EndDate DateTime
	, @CreUserEmpID INT 
AS
SET NOCOUNT ON
BEGIN	
    DECLARE @TStatus TABLE(StatusID INT PRIMARY KEY)
	DECLARE @TCategory TABLE(CategoryID INT PRIMARY KEY)
	DECLARE @TPriority TABLE(PriorityID INT PRIMARY KEY)

	IF (@Status IS NOT NULL)
	BEGIN
		INSERT INTO @TStatus(StatusID)
		SELECT DataTable.ItemCol.value('C1[1]','int')
		FROM @Status.nodes('//T/R') AS DataTable(ItemCol)
	END
	ELSE
	BEGIN
		INSERT INTO @TStatus(StatusID)
		SELECT DISTINCT l.LookupID FROM [Lookup] l
		INNER JOIN LookupType lt ON l.Type = lt.LookupTypeID	
		WHERE  lt.Code = 'TaskStatus'
	END

	IF (@Category IS NOT NULL)
	BEGIN
		INSERT INTO @TCategory(CategoryID)
		SELECT DataTable.ItemCol.value('C1[1]','int')
		FROM @Category.nodes('//T/R') AS DataTable(ItemCol)
	END
	ELSE
	BEGIN
		INSERT INTO @TCategory(CategoryID)
		SELECT ToDoCategoryId From ToDoCategory
	END

	IF (@Priority IS NOT NULL)
	BEGIN
		INSERT INTO @TPriority(PriorityID)
		SELECT DataTable.ItemCol.value('C1[1]','int')
		FROM @Priority.nodes('//T/R') AS DataTable(ItemCol)
	END
	ELSE
	BEGIN
		INSERT INTO @TPriority(PriorityID)
		SELECT DISTINCT l.LookupID FROM [Lookup] l
		INNER JOIN LookupType lt ON l.Type = lt.LookupTypeID	
		WHERE  lt.Code = 'TaskPriority'
	END

	SELECT 
	('P' + CAST(p.ProjectID as Varchar(10))) AS ID,
	p.ProjectID,
	0 AS TaskID,
	p.Name,
	p.Detail,
	p.StartDate,
	p.EndDate,
	GetDate() AS AlertDate,
	p.PriorityId as PriorityId,
	lp.Type as PriorityType, 
	lp.Code as PriorityCode, 
	lp.Text as PriorityText,
	p.StatusId as StatusId,
	ls.Type as StatusType, 
	ls.Code AS StatusCode,
	ls.Text AS StatusText,
	p.CategoryID as CategoryID, 
	lc.ToDoCategoryID as CategoryType, 
	lc.Code AS CategoryCode,
	lc.Name AS CategoryText,
	p.Pecentage AS Complete, 
	null AS Weightage, 
	null AS ParentID , 
	0 AS Type , 
	p.CustomerID, 
	c.FirstName + ' ' + c.LastName AS CustomerName,
	p.CustomerLocationID, 
	l.Name AS LocationName,
	ISNULL(c.FirstName,'') + ' ' + ISNULL(c.LastName,'') + ' ' + ISNULL(l.Name,'') AS Assosiation
	FROM Project p
	INNER JOIN [ToDoCategory] lc on p.CategoryID = lc.ToDoCategoryID
	INNER JOIN [Lookup] ls on p.StatusId = ls.LookupID
	INNER JOIN [Lookup] lp on p.PriorityId = lp.LookupID
	INNER JOIN @TCategory lct ON  p.CategoryID = lct.CategoryID
	INNER JOIN @TStatus lcs ON  p.StatusId = lcs.StatusID
	INNER JOIN @TPriority lcp ON  p.PriorityID = lcp.PriorityID
	LEFT OUTER JOIN Customer c on p.CustomerID = c.CustomerID
	LEFT OUTER JOIN CustomerLocation l on p.CustomerLocationID = l.CustomerLocationID
	WHERE p.EmployeeID = @EmpID AND p.IsInActive = 0 
	AND (@ProjectName IS NULL OR (p.Name LIKE '%' + @ProjectName + '%' OR p.Detail LIKE '%' + @ProjectName + '%'))
	AND (@StartDate IS NULL OR p.StartDate >= @StartDate)
	AND (@EndDate IS NULL OR (p.EndDate IS NULL OR p.EndDate <= @EndDate))
	AND (((@IsAdvanceSearch IS NULL OR @IsAdvanceSearch = 0) AND p.Pecentage < 100) OR @IsAdvanceSearch = 1 )
	UNION ALL
	SELECT ('T' + CAST(t.TaskId as Varchar(10))) AS ID,t.ProjectID AS ProjectID,t.TaskId, 
	t.Name,t.Notes,t.StartDate,t.EndDate,AlertDate,
	t.PriorityId,lp.Type as PriorityType,lp.Code AS PriorityCode,lp.Text AS PriorityText,
	t.StatusId,ls.Type AS StatusType,ls.Code AS StatusCode,ls.Text AS StatusText,
	0 as CategoryID, '' as CategoryType, '' AS CategoryCode,'' AS CategoryText,
	t.Pecentage AS Complete, t.Weigtage AS Weightage, ('P' + CAST(p.ProjectID as Varchar(10)))  As ParentID, 1 AS Type,
	0 AS CustomerID, ''  AS CustomerName,
	0 AS LocationID, '' AS LocationName, '' AS Assosiation
	FROM Project p
	INNER JOIN Task t on t.ProjectId = p.ProjectId
	INNER JOIN [Lookup] lp on t.PriorityId = lp.LookupID
	INNER JOIN [Lookup] ls on t.StatusId = ls.LookupID
	INNER JOIN @TCategory lct ON  p.CategoryID = lct.CategoryID
	INNER JOIN @TStatus lcs ON  t.StatusId = lcs.StatusID
	INNER JOIN @TPriority lcp ON  t.PriorityID = lcp.PriorityID
	WHERE p.EmployeeID = @EmpID AND p.IsInActive = 0  AND t.IsInActive = 0
	AND (@ProjectName IS NULL OR (p.Name LIKE '%' + @ProjectName + '%' OR p.Detail LIKE '%' + @ProjectName + '%'))
	AND (@StartDate IS NULL OR p.StartDate >= @StartDate)
	AND (@EndDate IS NULL OR (p.EndDate IS NULL OR p.EndDate <= @EndDate))
	AND (((@IsAdvanceSearch IS NULL OR @IsAdvanceSearch = 0) AND p.Pecentage < 100) OR @IsAdvanceSearch = 1 )
END

GO