Unexpected style:NSTableViewStylePlain for NSOutlineView?

Hello, Apple, We got a strange exception from one mac machine:

 System Version:	macOS 11.0 (20A5343j)
 Kernel Version:	Darwin 20.0.0
 Model Identifier:	MacBookAir7,2
 Processor Name:	Dual-Core Intel Core i5
 Processor Speed:	1.8 GHz
 Number of Processors:	1
 Total Number of Cores:	2
 L2 Cache (per Core):	256 KB
 L3 Cache:	3 MB
 Hyper-Threading Technology:	Enabled
 Memory:	8 GB
-[WBXMeetingApp exceptionHandler:shouldHandleException:mask:],Unexpected style.
0  Meeting Center           0x000000010fcedfd0 -[WBXMeetingApp exceptionHandler:shouldHandleException:mask:] + 119
1  ExceptionHandling          0x00007fff2cfdef31 -[NSExceptionHandler _handleException:mask:] + 364
2  ExceptionHandling          0x00007fff2cfdeb7c NSExceptionHandlerExceptionRaiser + 140
3  libobjc.A.dylib           0x00007fff6a8dd6f4 objc_exception_throw + 48
4  CoreFoundation           0x00007fff2a887c36 +[NSException raise:format:arguments:] + 88
5  Foundation             0x00007fff2d28a489 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 191
6  AppKit               0x00007fff27cf8d1b -[NSTableView _setStyleDataFromStyle:doUpdates:] + 168
7  wbxuikit              0x0000000114390a08 -[WBXPhoneNumberPickerView outlineView] + 367

Here is our code block:

- (NSOutlineView*)outlineView
{
	if ( !_outlineView )
	{
		_outlineView = [[NSOutlineView alloc] initWithFrame:self.scrollView.bounds];
		_outlineView.columnAutoresizingStyle = NSTableViewSequentialColumnAutoresizingStyle;
		_outlineView.headerView = nil;
		_outlineView.indentationPerLevel = 0;
		_outlineView.backgroundColor = NSColor.clearColor;
    if (@available(macOS 11.0, *)) {
      _outlineView.style = NSTableViewStylePlain;
      _outlineView.intercellSpacing = NSMakeSize(0, 0);
    } else {
      // Fallback on earlier versions
    }
		
		NSTableColumn* phoneNumberColumn = [[NSTableColumn alloc] initWithIdentifier:@"id_col_phoneNumber"];
		phoneNumberColumn.title = @"Flags";
		phoneNumberColumn.resizingMask = NSTableColumnAutoresizingMask;
		phoneNumberColumn.width = NSWidth(self.bounds)-3;
		phoneNumberColumn.editable = NO;
		[_outlineView addTableColumn:phoneNumberColumn];
	}
	return _outlineView;
}

So far, we only received one user exception report about it. Could you help us to identify why we got this exception on this user's machine? Can we set NSTableViewStylePlain for NSOutlineView?

Unexpected style:NSTableViewStylePlain for NSOutlineView?
 
 
Q