Null values returned from a cursor

I have a method below

public Date getLastPaidInvoiceDate(int id)


{
     String selectQuery =" SELECT  max(Rental_invoices.enddate) as DD from Rental_invoices "+
                           " where  Rental_invoices._id in(select invoice_id from RentalPayments)"+
                           " and Rental_invoices.tenancy_id"+"="+ id;

  Log.e("sql",selectQuery);

SQLiteDatabase db = this.getReadableDatabase();     
Cursor c = db.rawQuery(selectQuery, null);
Date d=null;
    if(c.moveToFirst()){
        try {
            d= fm.parse(c.getString(c.getColumnIndex("DD")));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    return d;
    }else
    {
    return null;
    }
}

If i print out the sql string and run it sqlite manager(fire fox), it returns the data i want.

Trying to use it code, i keep getting null pointer exception err as below

12-29 04:30:14.923: W/System.err(2017): java.lang.NullPointerException
12-29 04:30:14.923: W/System.err(2017):     at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1009)
12-29 04:30:14.923: W/System.err(2017):     at java.text.DateFormat.parse(DateFormat.java:553)
12-29 04:30:14.943: W/System.err(2017):     at meter.manager.helper.DatabaseHelperClass.getLastPaidInvoiceDate(DatabaseHelperClass.java:2726)
12-29 04:30:14.943: W/System.err(2017):     at com.example.metermanager.SetInActiveTenant.UpDate(SetInActiveTenant.java:79)
12-29 04:30:14.943: W/System.err(2017):     at java.lang.reflect.Method.invokeNative(Native Method)
12-29 04:30:14.943: W/System.err(2017):     at java.lang.reflect.Method.invoke(Method.java:515)
12-29 04:30:14.943: W/System.err(2017):     at android.view.View$1.onClick(View.java:3818)
12-29 04:30:14.943: W/System.err(2017):     at android.view.View.performClick(View.java:4438)
12-29 04:30:14.943: W/System.err(2017):     at android.view.View$PerformClick.run(View.java:18422)
12-29 04:30:14.943: W/System.err(2017):     at android.os.Handler.handleCallback(Handler.java:733)
12-29 04:30:14.943: W/System.err(2017):     at android.os.Handler.dispatchMessage(Handler.java:95)
12-29 04:30:14.943: W/System.err(2017):     at android.os.Looper.loop(Looper.java:136)
12-29 04:30:14.943: W/System.err(2017):     at android.app.ActivityThread.main(ActivityThread.java:5017)
12-29 04:30:14.943: W/System.err(2017):     at java.lang.reflect.Method.invokeNative(Native Method)
12-29 04:30:14.943: W/System.err(2017):     at java.lang.reflect.Method.invoke(Method.java:515)
12-29 04:30:14.943: W/System.err(2017):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
12-29 04:30:14.943: W/System.err(2017):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
12-29 04:30:14.943: W/System.err(2017):     at dalvik.system.NativeStart.main(Native Method)

This is how i use in code

Date d=db.getLastPaidInvoiceDate(id);

Any reason why?