DataGrid Selected list and TBookmark

Delphi 11.1

FMX

Firepower

Have a datagrid with embedded switch to select records.  Was using 'var bm  : tBookMark' to iterate through selected records in grid without any problems.  Have introduced a new component into the project 'PDFium' and now tBookmark no longer wants to work and comes up with error:

[dcc32 Error] Main.pas(2111): E2010 Incompatible types: 'TBookmark' and 'System.TArray<System.Byte>'

Has anybody had a similar problem and how is the problem fixed - apart from not using PDFium which I don't want to do as I like what this component can do.

Any help would be appreciated.

Bill