Undefined offset in checkbox dynamic field

I have a dynamic field where user can add as many rows as it wants. There are 3 checkboxs in each row. after user added as much as they wanted they click a button and get sent to FgProcess.php.

FgTable.php

<script>
var FgRow = 0;
function addfg()
{
    FgRow++;
    var html = "<tr>";
        html += "<td><input type='text' name='SKUDescription[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='LotNumber[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='BBD[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='Size[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='SizeUOM[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='UnitsPerCase[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='CaseCount[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='CasePartial[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='UnitsDamaged[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='UnitsLeak[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='UnitsSample[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='UnitTotal[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='NetWeightTotal[]' class ='form-control'/></td>";
        html += "<td><input type='text' name='ProductTemperature[]' class ='form-control'/></td>";
        html += "<td><input type='checkbox' name='Organic[]' value='1' class='custom-checkbox'/></td>";
        html += "<td><input type='checkbox' name='OnHold[]' value='1' class='custom-checkbox'/></td>";
        html += "<td><input type='checkbox' name='WIP[]' value='1' class='custom-checkbox'/></td>";
        html += "<td style='width: 2%'></td>";
        html += "</tr>";
        
        document.getElementById("finishedgoods_row").insertRow().innerHTML = html;
}

My Problem is that I get an offset error when user does not check the checkboxes. I know the reason is that if not checked the value is NULL.

I tried fixing this issue by adding hidden input for each of my checkboxes but then I got extra checkbox values sometimes!

FgProcess.php

if (isset($_POST['fgAdd']))
{
    $WOID = $_POST['id'];
    print_r($_POST);

    for ($i = 0; $i < count($_POST["SKUDescription"]); $i++)
    {
        $SKUDescription = $_POST["SKUDescription"][$i];
        $LotNumber = $_POST["LotNumber"][$i];
        $BBD = $_POST["BBD"][$i];
        $Size = $_POST["Size"][$i];
        $SizeUOM = $_POST["SizeUOM"][$i];
        $UnitsPerCase = $_POST["UnitsPerCase"][$i];
        $CaseCount = $_POST["CaseCount"][$i];
        $CasePartial = $_POST["CasePartial"][$i];
        $UnitsDamaged = $_POST["UnitsDamaged"][$i];
        $UnitsLeak = $_POST["UnitsLeak"][$i];
        $UnitsSample = $_POST["UnitsSample"][$i];
        $UnitTotal = $_POST["UnitTotal"][$i];
        $NetWeightTotal = $_POST["NetWeightTotal"][$i];
        $ProductTemperature = $_POST["ProductTemperature"][$i];

        if ($_POST["Organic"][$i]==null){$Organic = '0';}else{$Organic = $_POST["Organic"][$i];}
        if ($_POST["OnHold"][$i]==null){$OnHold = '0';}else{$OnHold = $_POST["OnHold"][$i];}
        if ($_POST["WIP"][$i]==null){$WIP = '0';}else{$WIP = $_POST["WIP"][$i];}
        //after this part insert into mysql and check errors and etc
    }
        //the rest of if statement

I tried checking for NULL but it didn't work. Each of these lines gave me a Undefined offset: 1 error.

if ($_POST["Organic"][$i]==null){$Organic = '0';}else{$Organic = $_POST["Organic"][$i];}
if ($_POST["OnHold"][$i]==null){$OnHold = '0';}else{$OnHold = $_POST["OnHold"][$i];}
if ($_POST["WIP"][$i]==null){$WIP = '0';}else{$WIP = $_POST["WIP"][$i];}

for example when i tried to add two rows, with the first row checkboxes being checked and then second row not being checked, this is what i get when print_r($_POST)

[Organic] => Array ( [0] => 1 ) [OnHold] => Array ( [0] => 1 ) [WIP] => Array ( [0] => 1 )

I know the problem is from checkboxes since i had no problem when the 3 checkboxes were text.

I would appreciate any help.