Sequelize conditional inclusion of where clause nodejs

I have this code, which has multiple where clause:

Time_Sheet_Details.findAll({
    include: [
        {
            model: timesheetNotesSubcon,
            required: false,
            attributes:["note","file_name", "id", "working_hrs", "timestamp", "has_screenshot", "notes_category"]
        },
        {
            model: Timesheet,
            attributes:["id","leads_id","userid"],
            where:  {leads_id: filters.leads_id}, // Client
            include:[
                {
                    model: Lead_Info, attributes:["id","fname","lname","email","hiring_coordinator_id","status"],
                    where:  {hiring_coordinator_id: {$in: filters.sc_id}}, // SC
                    include:[{
                        model: adminInfoSchema,
                        required: false,
                        attributes:["admin_id","admin_fname", "admin_lname", "admin_email", "signature_contact_nos", "signature_company"],      
                    }]

                },
                {
                    model:Personal_Info,attributes:["userid","fname","lname","email"],
                    where: {userid: filters.subcon_id}, // Subcon
                }
            ]
        }],
    where: { 
        reference_date: filters.reference_date
    },
    order:[
        ["id","DESC"]
    ],
    offset:((page-1)*limit),
    limit : limit,
    subQuery:false

}).then(function(foundObject){
    willFulfillDeferred.resolve(foundObject);
});

The where clause is the one with the comment Client, SC and Subcon. However, what is the best approach if those where clause is optional? I am using that for search filter. So if filters.leads_id is null then the where: {leads_id: filters.leads_id}, // Client should not be included in the query. Same with the others. The only solution I can think of is repeat those code blocks for each scenario of not null parameters but that's to repetitive and not practical.

Any other approach or solutions?

via Yassi