Overflow error in exoquant color reduction library from github

Private Function MakeHash(ByVal rgba As Uinteger) As UInteger
            Try
                '1
                rgba -= (rgba >> 13) Or (rgba << 19)
                '2
                rgba -= (rgba >> 13) Or (rgba << 19)
                '3
                rgba -= (rgba >> 13) Or (rgba << 19)
                rgba -= (rgba >> 13) Or (rgba << 19)
                rgba -= (rgba >> 13) Or (rgba << 19)
                rgba = rgba And (EXQ_HASH_SIZE - 1)
                Return rgba
            Catch ex As Exception
                MessageBox.Show("ExoQuant.MakeHash: " + ex.Message + " " + ex.StackTrace)
                Return 255
            End Try
        End Function

Public Sub Feed(ByVal pData As Byte())
            Dim channelMask As Byte = &HFF00 >> pExq.numBitsPerChannel
            Dim nPixels As Integer = Int(pData.Length / 4)

            For i As Integer = 0 To nPixels - 1
                Dim r As Byte = pData(i * 4 + 0),
                    g As Byte = pData(i * 4 + 1),
                    b As Byte = pData(i * 4 + 2),
                    a As Byte = pData(i * 4 + 3)
                'If pdata(i * 4 + 3) = 0 Then
                '    a = 255
                'Else
                '    a = pData(i * 4 + 3)
                'End If
                Dim hash As UInteger = MakeHash(ToRGBA(r, g, b, a))
                Dim pCur As ExqHistogramEntry = pExq.pHash(hash)

                While pCur IsNot Nothing AndAlso (pCur.ored <> r OrElse pCur.ogreen <> g OrElse pCur.oblue <> b OrElse pCur.oalpha <> a)
                    pCur = pCur.pNextInHash
                End While

                If pCur IsNot Nothing Then
                    pCur.num += 1
                Else
                    pCur = New ExqHistogramEntry()
                    pCur.pNextInHash = pExq.pHash(hash)
                    pExq.pHash(hash) = pCur
                    pCur.ored = r
                    pCur.ogreen = g
                    pCur.oblue = b
                    pCur.oalpha = a
                    r = r And channelMask
                    g = g And channelMask
                    b = b And channelMask
                    pCur.color.r = r / 255.0F * SCALE_R
                    pCur.color.g = g / 255.0F * SCALE_G
                    pCur.color.b = b / 255.0F * SCALE_B
                    pCur.color.a = a / 255.0F * SCALE_A

                    If pExq.transparency Then
                        pCur.color.r *= pCur.color.a
                        pCur.color.g *= pCur.color.a
                        pCur.color.b *= pCur.color.a
                    End If

                    pCur.num = 1
                    pCur.palIndex = -1
                    pCur.ditherScale.r = -1
                    pCur.ditherScale.g = -1
                    pCur.ditherScale.b = -1
                    pCur.ditherScale.a = -1
                    pCur.ditherIndex(0) = -1
                    pCur.ditherIndex(1) = -1
                    pCur.ditherIndex(2) = -1
                    pCur.ditherIndex(3) = -1
                End If
            Next
        End Sub

Private Function ToRGBA(ByVal r As UInteger, ByVal g As UInteger, ByVal b As UInteger, ByVal a As UInteger) As UInteger
         Return r Or (g << 8) Or (b << 16) Or (a << 24)
     End Function