...
        sql = "SELECT logID, if(projectLog.distance=0, NULL," & _
          "projectLog.distance) AS 'Entfernung' FROM  projectLog "
        Try
            'Grid füllen
            Dim da As New MySqlDataAdapter(sql, conn)
            Dim ds As New DataSet
            da.Fill(ds)
            Dim dv As New DataView(ds.Tables(0))
            dgvData.DataSource = dv 
        ...

 sql = "SELECT logID, if(rideTime=MAKETIME(0,0,0), NULL, rideTime) AS" & _
   "'Fahrzeit' FROM  projectLog "

   Private Sub dgvData_CellFormatting(sender As Object, e As _
     System.Windows.Forms.DataGridViewCellFormattingEventArgs) _
        Handles dgvData.CellFormatting
        Try
            If DirectCast(e.Value, System.TimeSpan) = New TimeSpan(0, 0, 0) Then
                e.Value = "" : e.FormattingApplied = True
            End If
        Catch ex As Exception
            MsgBox("Spalte / Zeile: " & e.ColumnIndex.ToString & " / " & _
              e.RowIndex.ToString & vbCrLf & e.DesiredType.FullName & vbCrLf & _
              e.Value.GetType.FullName & vbCrLf & e.Value.ToString & vbCrLf & _
              ex.Message)
        End Try
    End Sub