cleanup: run XCode code analysis

enable ARC in CMakelist.txt
fix small potentials leaks across the client

Refs #75600

Change-Id: I72ba17e6daed393abdf38653f45c040bd3427ead
diff --git a/src/QNSTreeController.mm b/src/QNSTreeController.mm
index eca4884..f7697fb 100644
--- a/src/QNSTreeController.mm
+++ b/src/QNSTreeController.mm
@@ -55,7 +55,7 @@
 
 - (id) initWithQModel:(QAbstractItemModel*) model
 {
-    [super init];
+    self = [super init];
     self->privateQModel = model;
 
     topNodes = [[NSMutableArray alloc] init];