fix: dangling reference crash in FreeSpaceLabel (#1604)

qt/FreeSpaceLabel.cc

@@ -73,12 +73,17 @@ void FreeSpaceLabel::onTimer()
 
     auto* q = new RpcQueue();
 
+    auto* alive = new bool(true);
+    connect(this, &QObject::destroyed, [alive] { *alive = false; });
+
     q->add([this, &args]()
         {
             return session_->exec("free-space", &args);
         });
 
-    q->add([this](RpcResponse const& r)
+    q->add([this, alive](RpcResponse const& r)
+        {
+            if (*alive)
             {
                 // update the label
                 auto const bytes = dictFind<int64_t>(r.args.get(), TR_KEY_size_bytes);
@@ -88,7 +93,7 @@ void FreeSpaceLabel::onTimer()
                 }
                 else
                 {
-                setText(QString());
+                    clear();
                 }
 
                 // update the tooltip
@@ -96,6 +101,9 @@ void FreeSpaceLabel::onTimer()
                 setToolTip(QDir::toNativeSeparators(path ? *path : QString()));
 
                 timer_.start();
+            }
+
+            delete alive;
         });
 
     q->run();