Insert Stored Procedure with null parameters

I want to create an insert stored procedure with null parameters, if pass the value for that parameter then it has to insert or update in database

My stored procedure is:

Create proc [dbo].[SP_InsertOrUpdateCourseDetails]
    @CourseID int,
    @Tab1Title nvarchar(250) = null,
    @Tab1Description nvarchar(max) = null,
    @Tab2Title nvarchar(250) = null,
    @Tab2Description nvarchar(max) = null,
    @Tab3Title nvarchar(250) = null,
    @Tab3Description nvarchar(max) = null,
    @Tab4Title nvarchar(250) = null,
    @Tab4Description nvarchar(max) = null,
    @Syllabus nvarchar(max) = null
As
Begin

    If NOT EXISTS (Select * from CourseDetail Where CourseID=@CourseID )
    Begin
        Insert into CourseDetail(CourseID, Tab1Title, Tab1Description, 
                                 Tab2Title, Tab2Description,
                                 Tab3Title, Tab3Description, Tab4Title, Tab4Description,
                                 Syllabus)
        values (@CourseID, @Tab1Title, @Tab1Description, @Tab2Title, @Tab2Description,
                @Tab3Title, @Tab3Description, @Tab4Title, @Tab4Description, @Syllabus)

        IF @@ERROR = 0 AND @@ROWCOUNT =1
        Begin
            Select top 1 CourseID from CourseDetail Order by CourseDetailID Desc
        End
        Else 
        Begin
             Select 0
        End
    End
 Else
 Begin
     Update CourseDetail 
     SET
        Tab1Title = @Tab1Title,
        Tab1Description = @Tab1Description,
        Tab2Title = @Tab2Title,
        Tab2Description = @Tab2Description,
        Tab3Title = @Tab3Title,
        Tab3Description = @Tab3Description,
                                                

                                                                                                        
                                                    
                                                
                                                

                                                    

                                                        
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