Access violation and Abstract error - delphi

Question

I have a TButton event handler which either throws an Access Violation or Abstract Error when the method has completed execution. Delphi then highlights end. in my project source file. The method runs successfully, deleting the correct row from the database.
I have components which are created at runtime. Each row contains a label, an 'update' button and a 'delete' button, which have the database row number they are associated with in their names. The event handler throwing the errors is for delete.
procedure TFormInventoryMngmnt.ProductDeleteClick(Sender: TObject);
var
button : TButton;
row : integer;
confirm : integer;
begin
// Assuming it is button..how else can this be called?
button := Sender as TButton;
// Get row
row := StrToInt(StringReplace(button.Name, 'Delete', '', [rfReplaceAll, rfIgnoreCase]));
// Confirm
confirm := MessageDlg('Are you sure?', mtInformation, [mbYes, mbNo], 0);
if confirm = mrYes then
begin
// Delete row
UnitSession.Query.SQL.Clear;
UnitSession.Query.SQL.Add(Format(' DELETE FROM Products WHERE Product_ID = %s ', [IntToStr(row)]));
UnitSession.Query.ExecSQL;
buildManagementSection;
end;
// FIXME: why is this throwing access / abstract violation
end;
If you need more code or explanations just leave a comment and I'll get back to you.
Thanks!
Updated with code for buildManagementSection
I commented out the call to buildManagementSection from the listener and it did not throw any exceptions. This error could be caused from the method below, but I've never had a problem with it until now.
procedure TFormInventoryMngmnt.buildManagementSection;
var
index : integer;
runningHeight : integer;
productName : TLabel;
productUpdate : TButton;
productDelete : TButton;
const
MARGIN_TOP = 35;
// Left value of labels
LABEL_LEFT = 0;
// Left value of update button
UPDATE_LEFT = 235;
// Left value of delete button
DELETE_LEFT = 315;
begin
// Run sql query
UnitSession.Query.SQL.Clear;
UnitSession.Query.SQL.Add('SELECT Product, Product_ID FROM Products ORDER BY Product_ID');
UnitSession.Query.Active := true;
// Remove all components in the manage section
for index := (ScrollBoxManage.ComponentCount - 1) downto 0 do
begin
ScrollBoxManage.Components[index].Free;
end;
// No items
if UnitSession.Query.RecordCount = 0 then
begin
productName := TLabel.Create(ScrollBoxManage);
productName.Parent := ScrollBoxManage;
productName.Caption := 'No items!';
productName.Font.Color := clRed;
productName.Visible := true;
exit;
end;
// Build form
UnitSession.Query.First;
runningHeight := 0;
for index := 0 to (UnitSession.Query.RecordCount - 1) do
begin
// Create components
productName := TLabel.Create(ScrollBoxManage);
productUpdate := TButton.Create(ScrollBoxManage);
productDelete := TButton.Create(ScrollBoxManage);
// Set parents
productName.Parent := ScrollBoxManage;
productUpdate.Parent := ScrollBoxManage;
productDelete.Parent := ScrollBoxManage;
// Set values
productName.Caption := UnitSession.Query.Fields[0].AsString;
productUpdate.Caption := 'Update';
productDelete.Caption := 'Delete';
// Set event handlers
productUpdate.OnClick := FormInventoryMngmnt.ProductUpdateClick;
productDelete.OnClick := FormInventoryMngmnt.ProductDeleteClick;
// Set top position
productName.Top := runningHeight + 3;
productUpdate.Top := runningHeight;
productDelete.Top := runningHeight;
// Set button association
productName.Name := 'Label' + UnitSession.Query.Fields[1].AsString;
productUpdate.Name := 'Update' + UnitSession.Query.Fields[1].AsString;
productDelete.Name := 'Delete' + UnitSession.Query.Fields[1].AsString;
// Set left position
productName.Left := LABEL_LEFT;
productUpdate.Left := UPDATE_LEFT;
productDelete.Left := DELETE_LEFT;
// Set as visible
productName.Visible := true;
productUpdate.Visible := true;
productDelete.Visible := true;
runningHeight := runningHeight + MARGIN_TOP;
UnitSession.Query.Next;
end;
end;

Answer 1

The button instance hasn't been created!
There is no need to say
button := Sender as Tbutton
just reference the original button in the code since it is in scope on the form
row := StrToInt(StringReplace(ProductDelete.Name, 'Delete', '', [rfReplaceAll, rfIgnoreCase]));
or do this
with TButton(sender) do
row := StrToInt(StringReplace(Name, 'Delete', '', [rfReplaceAll, rfIgnoreCase]));
Or if you really want to do it this way, with a variable holding the button instance, then
you must create it first
begin
button := TButton.Create(Self);
try
button := TButton(Sender)
// your code
finally
button.Free
end
end