How can I fix this warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given

<?php

session_start();

//First cari fail untuk connection ke database
include_once ("./includes/dbconnection.php");

if (isset($_POST['submit'])){
$namakoperasi = mysqli_real_escape_string($conn, $_POST['namakoperasi']);
$jenis2 = mysqli_real_escape_string($conn, $_POST['jenis2']);
$tarikh = mysqli_real_escape_string($conn, $_POST['tarikh']);

if ($jenis2 == 'Resit') {
?>







<?php
$sql = "SELECT * FROM receipt WHERE RecDate = '".$tarikh."' AND cooperasiId = '".$namakoperasi."' ";
$result = mysqli_query($conn, $sql);

while ($receipt = mysqli_fetch_array($result)) {
$resitdate = $receipt['RecDate'];
$resitno = $receipt['RecNo'];
$resitnama = $receipt['coopName'];
$resitamaun= $receipt['Recamount'];
$resitakaun= $receipt['Recakaun'];

echo "

";
}
?>

Tarikh	No Resit	Nama Koperasi	Jumlah (RM)	Akaun
".$resitdate."	".$resitno."	".$resitnama."	".$resitamaun."	".$resitakaun."

<?php
} else {
if ($jenis2 == 'Baucer') {
?>








<?php
$sql = "SELECT * FROM baucer WHERE cooperasiId = '".$namakoperasi."' and BauDate = '".$tarikh."'";
$result = mysqli_query($conn, $sql);

while ($baucer = mysqli_fetch_array($result)) {
$baucerdate = $baucer['BauDate'];
$baucerno = $baucer['BauNo'];
$baucernama = $baucer['coopName'];
$baucerakaun = $baucer['BauAkaun'];
$bauceramaun= $baucer['BauAmaun'];
$baucernocek= $baucer['Baunocek'];

echo "

";
}
?>

Tarikh	No Baucer	Nama Koperasi	Akaun	Jumlah (RM)	Nota/No cek
".$baucerdate."	".$baucerno."	".$baucernama."	".$baucerakaun."	".$bauceramaun."	".$baucernocek."

<?php
} else {
if ($jenis2 == 'InvoisJualan') {
?>






<?php

$sql = "SELECT coop01.coopId, coop01.coopName, invoisjualan.i_j_No, invoisjualan.i_j_date, invoisjualan.i_j_jumlah,
invoisjualan.i_j_nota, invoisjualan.coopId, invoisjualan.staffUsername

FROM invoisjualan
LEFT JOIN coop01 ON invoisjualan.coopId = coop01.coopId

WHERE i_j_date = '.$tarikh.' AND coopId = '.$namakoperasi.'
";

$result = mysqli_query($conn, $sql);

while ($invoisjualan = mysqli_fetch_array($result)) {
$noinvj = $invoisjualan['noinvj'];
$tarikhinvj = $invoisjualan['tarikhinvj'];
$amauninvj = $invoisjualan['amauninvj'];
$notainvj= $invoisjualan['notainvj'];
$namakoperasi = $invoisjualan['namakoperasi'];

echo "

";



}
?>

Tarikh	No Invois	Nama Koperasi	Jumlah (RM)	Nota
".$noinvj."	".$tarikhinvj."	".$amauninvj."	".$notainvj."	".$namakoperasi."

<?php
} else {
if ($jenis2 == 'InvoisBelian') {
?>






<?php
$sql = "SELECT * FROM invoisbelian WHERE cooperasiId = '".$namakoperasi."' and BauDate = '".$tarikh."' ";
$result = mysqli_query($conn, $sql);

while ($invoisbelian = mysqli_fetch_array($result)) {
$invbdate = $invoisbelian['invbdate'];
$invbno = $invoisbelian['invbNo'];
$invbnama = $invoisbelian['coopName'];
$invbamaun= $invoisbelian['invbamaun'];
$invbnote= $invoisbelian['invbnote'];

echo "

";
}
?>

Tarikh	No Invois	Nama Koperasi	Jumlah (RM)	Nota
".$invbdate."	".$invbno."	".$invbnama."	".$invbamaun."	".$invbnote."

<?php

}
}
}
}

}

?>