I can see all the Objectives in the list that don’t have a parent, as expected, and I can display all those that have children. However, I encounter an error when attempting to compact anyone with children.

struct ObjectiveTable: View{
    @Query(filter: #Predicate<Objective>{$0.parent == nil}) var all : [Objective]
    @State var selected : Objective?

    
    var body: some View{
        VStack{
            List(all ,children: Objective.sonsNIL){ line  in
                    Text(line.name)
            }
        }
    }
}
@Model
final class Objective{

    @Attribute(.unique)
    var id =  UUID()
    var name: String
    var parent: Objective? = nil
    @Relationship(deleteRule: .cascade, inverse: Objective.parent)
    var sons: [Objective] = []

    var sonsNIL: [Objective]?{
        get{
            if sons.count < 1{
                return nil
            } else{
                return sons
            }
        }
    }
...

Row index -1 out of row range (numberOfRows: 9) for <SwiftUI.SwiftUIOutlineListView: 0x112087000>
(
    0   CoreFoundation                      0x000000018c834ec0 __exceptionPreprocess + 176
    1   libobjc.A.dylib                     0x000000018c31acd8 objc_exception_throw + 88
    2   AppKit                              0x00000001903eb304 -[NSTableRowData _availableRowViewWhileUpdatingAtRow:] + 0
    3   SwiftUI                             0x00000001bb365224 $s7SwiftUI0A17UIOutlineListViewC11removeItems2at8inParent13withAnimationy10Foundation8IndexSetV_ypSgSo07NSTableeL7OptionsVtF + 1388
    4   SwiftUI                             0x00000001bb3656f8 $s7SwiftUI0A17UIOutlineListViewC11removeItems2at8inParent13withAnimationy10Foundation8IndexSetV_ypSgSo07NSTableeL7OptionsVtFTo + 252
    5   CoreFoundation                      0x000000018c7a28b4 __invoking___ + 148
    6   CoreFoundation                      0x000000018c7a272c -[NSInvocation invoke] + 428
    7   CoreFoundation                      0x000000018c7d7958 -[NSInvocation invokeWithTarget:] + 64
    8   AppKit                              0x000000019052a110 -[_NSObjectAnimator forwardInvocation:] + 1512
    9   CoreFoundation                      0x000000018c7a0ee4 ___forwarding___ + 964
    10  CoreFoundation                      0x000000018c7a0a60 _CF_forwarding_prep_0 + 96
    11  SwiftUI                             0x00000001bb37e458 $s7SwiftUI22OutlineListCoordinatorC19recursivelyDiffRows_4with2by9expandAllyAA0a9UIOutlineD4ViewC_AA0dC4ItemCAA0nD4TreeVAA14ExpansionStateOtF + 37012
    12  SwiftUI                             0x00000001bb3802b8 $s7SwiftUI22OutlineListCoordinatorC19recursivelyDiffRows_4with2by9expandAllyAA0a9UIOutlineD4ViewC_AA0dC4ItemCAA0nD4TreeVAA14ExpansionStateOtF + 44788
    13  SwiftUI                             0x00000001bb37538c $s7SwiftUI22OutlineListCoordinatorC8diffRows2of2toyAA0a9UIOutlineD4ViewC_AA0kD4TreeVtF + 120
    14  SwiftUI                             0x00000001bb36f3d4 $s7SwiftUI22OutlineListCoordinatorC6update4diff04viewD4Tree18idSelectionChanged010navigationk4SeedL0011templateRowL011transactionySb_AA04ViewdI0VS3bAA11TransactionVtFyycfU_yyXEfU_ + 220
    15  SwiftUI                             0x00000001bb369044 $s7SwiftUI22OutlineListCoordinatorC24withSelectionUpdateGuard33_BE7B171B0BEE2A9E27ED12968C3771F8LLyySS_yyXEtF + 1320
    16  SwiftUI                             0x00000001bb36f2d4 $s7SwiftUI22OutlineListCoordinatorC6update4diff04viewD4Tree18idSelectionChanged010navigationk4SeedL0011templateRowL011transactionySb_AA04ViewdI0VS3bAA11TransactionVtFyycfU_ + 708
    17  SwiftUICore                         0x00000002277cb578 $sIeg_ytIegr_TRTA + 28
    18  SwiftUICore                         0x0000000227a6d2b8 $s7SwiftUI6UpdateO15dispatchActionsyyFZ + 1236
    19  SwiftUICore                         0x0000000227a6c79c $s7SwiftUI6UpdateO3endyyFZ + 212
    20  SwiftUICore                         0x0000000227f6061c $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_Tf4ddd_n + 176
    21  CoreFoundation                      0x000000018c7c17a8 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 36
    22  CoreFoundation                      0x000000018c7c1694 __CFRunLoopDoObservers + 552
    23  CoreFoundation                      0x000000018c7c0380 CFRunLoopRunSpecific + 648
    24  HIToolbox                           0x0000000197c000cc RunCurrentEventLoopInMode + 292
    25  HIToolbox                           0x0000000197c05d1c ReceiveNextEventCommon + 220
    26  HIToolbox                           0x0000000197c06020 _BlockUntilNextEventMatchingListInModeWithFilter + 76
    27  AppKit                              0x0000000190303650 _DPSNextEvent + 660
    28  AppKit                              0x0000000190c2a408 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 688
    29  AppKit                              0x00000001902f675c -[NSApplication run] + 480
    30  AppKit                              0x00000001902cd02c NSApplicationMain + 888
    31  SwiftUI                             0x00000001ba77045c $s7SwiftUI6runAppys5NeverOSo21NSApplicationDelegate_So11NSResponderCXcFTf4e_nAA07TestingdG0C_Tg5Tm + 160
    32  SwiftUI                             0x00000001babf4854 $s7SwiftUI6runAppys5NeverOxAA0D0RzlF + 84
    33  SwiftUI                             0x00000001baf04134 $s7SwiftUI3AppPAAE4mainyyFZ + 224
    34  Marlo SystemManagement.debug.dylib  0x0000000104c5e108 $s22Marlo_SystemManagement0a1_bC3AppV5$mainyyFZ + 40
    35  Marlo SystemManagement.debug.dylib  0x0000000104c5e1d4 __debug_main_executable_dylib_entry_point + 12
    36  dyld                                0x000000018c358274 start + 2840
)
FAULT: NSTableViewException: Row index -1 out of row range (numberOfRows: 9) for <SwiftUI.SwiftUIOutlineListView: 0x112087000>; (user info absent)`