I have one line (1193) in a data transfer that is not occurring

All the other data transfer occurs without fault. However, there is no data in strChangeProposed and it is a longtext field (Access) as is the field strRequirements.

Code:
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strRequirements = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strChangeProposed
The error mentions that the field is DBNull. Why is that a problem? The input table fields will not always have data in them and I want the transfer to take place anyway.

Name: error.jpg Views: 632 Size: 55.7 KB

Whole Routine:

Code:
    Private Sub SaveRevChangeRequest()
        Try
            'Assign values to global variables from form controls and save changes to Change Request
            glbstrBaseCategory = CStr(lblChangeType.Text)
            glbstrFilePath = CStr(lblEFile.Text)
            glbblnSaved = True
            Me.Validate()
            Me.LnkChangeRequestBindingSource.EndEdit()
            Me.LnkChangeRequestTableAdapter.Update(Me._MasterBase4_0ItemMasterDataSet)
            'Update Change ID
            Me.LkpChangeIDTableAdapter.Fill(Me._MasterBase4_0ItemMasterDataSet.lkpChangeID)
            Me._MasterBase4_0ItemMasterDataSet.lkpChangeID(0).intChangeID = glbintCRNum
            Me.Validate()
            Me.lkpChangeIDBindingSource.EndEdit()
            Me.LkpChangeIDTableAdapter.Update(Me._MasterBase4_0ItemMasterDataSet)
            'Update Item Record
            Me.LnkChangeRequestTableAdapter.FillByChangeNum(Me._MasterBase4_0ItemMasterDataSet.lnkChangeRequest, glbintCRNum)
            Me.TblItemMasterTableAdapter.FillBySiTechID(Me._MasterBase4_0ItemMasterDataSet.tblItemMaster, glbintIDNum)
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strTitle = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strTitle
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strRevision = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strRevision
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strRequirements = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strChangeProposed
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strOwner = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strOwner
            _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).strWhereUsed = _MasterBase4_0ItemMasterDataSet.lnkChangeRequest(0).strWhere
            If glbblnEffective Then
                _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).blnEffective = False
                _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).blnObsolete = False
                _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).blnSupersede = True
                _MasterBase4_0ItemMasterDataSet.tblItemMaster(0).blnValidated = False
            End If
            Me.tblItemMasterBindingSource.EndEdit()
            Me.TblItemMasterTableAdapter.Update(Me._MasterBase4_0ItemMasterDataSet)
        Catch ex As Exception
            MessageBox.Show(String.Format("Message: {0} {1} StackTrace: {2}", ex.Message, vbNewLine, ex.StackTrace))
            'Me.Close()
            'mnuItemMaster.Show()
        End Try
    End Sub