Don't leak sort descriptors array in wxDataViewCtrl in wxOSX.

wxCocoaOutlineDataSource owns its sortDescriptors field, so it must release it
in its dealloc() (and also initialize it in its init(), no idea how did it
work without this being done before).

Closes #16231.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76642 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/cocoa/dataview.mm

@@ -495,6 +495,8 @@ initWithModelPtr:(wxDataViewModel*)initModelPtr
 
         currentParentItem = nil;
 
+        sortDescriptors = nil;
+
         children = [[NSMutableArray alloc] init];
         items    = [[NSMutableSet   alloc] init];
     }
@@ -503,6 +505,8 @@ initWithModelPtr:(wxDataViewModel*)initModelPtr
 
 -(void) dealloc
 {
+    [sortDescriptors release];
+
     [currentParentItem release];
 
     [children release];