fix crash (#1587)

(cherry picked from commit 9fc8054)

Author: kaichie

rviz_common/src/rviz_common/properties/property_tree_widget.cpp

@@ -103,7 +103,7 @@ void PropertyTreeWidget::setModel(PropertyTreeModel * model)
   if (model_) {
     connect(
       model_, SIGNAL(propertyHiddenChanged(const Property*)),
-      this, SLOT(propertyHiddenChanged(const Property*)), Qt::QueuedConnection);
+      this, SLOT(propertyHiddenChanged(const Property*)), Qt::DirectConnection);
     connect(
       model_, SIGNAL(expand(const QModelIndex&)),
       this, SLOT(expand(const QModelIndex&)));
@@ -119,12 +119,14 @@ void PropertyTreeWidget::setModel(PropertyTreeModel * model)
 void PropertyTreeWidget::propertyHiddenChanged(const Property * property)
 {
   if (model_) {
-    const auto & parent_index = model_->parentIndex(property);
-    if (parent_index.isValid()) {
-      setRowHidden(property->rowNumberInParent(), parent_index, property->getHidden());
-    } else {
-      printf("Trying to hide property '%s' that is not part of the model.\n",
-        qPrintable(property->getName()));
+    if (property->parent() != nullptr) {
+      const auto & parent_index = model_->parentIndex(property);
+      if (parent_index.isValid()) {
+        setRowHidden(property->rowNumberInParent(), parent_index, property->getHidden());
+      } else {
+        printf("Trying to hide property '%s' that is not part of the model.\n",
+          qPrintable(property->getName()));
+      }
     }
   }
 }