Add mutex for `JobOperationHistory` (Issue #819)
Port of !304 (closed) to new ThunarJobOperationHistory
@hi-im-buggy : I added you as co-author and as well took the style-fix commit. Fine like that for you ?
Port of !304 (closed) to new ThunarJobOperationHistory
@hi-im-buggy : I added you as co-author and as well took the style-fix commit. Fine like that for you ?