ProjectTree: Fix soft assert

Fix soft assert when accessing the lone project file node in a project
that failed to parse.

Change-Id: I73d9b0012292dd5516a0a9c81cdc4003eebf2a92
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/projectexplorer/projectmodels.cpp

@@ -210,6 +210,7 @@ void FlatModel::addOrRebuildProjectModel(Project *project)
     WrapperNode *container = nodeForProject(project);
     if (container) {
         container->removeChildren();
+        project->containerNode()->removeAllChildren();
     } else {
         container = new WrapperNode(project->containerNode());
         rootItem()->insertOrderedChild(container, &compareProjectNames);
@@ -224,6 +225,7 @@ void FlatModel::addOrRebuildProjectModel(Project *project)
     }
     if (container->childCount() == 0) {
         FileNode *projectFileNode = new FileNode(project->projectFilePath(), FileType::Project, false);
+        project->containerNode()->addNestedNode(projectFileNode);
         seen.insert(projectFileNode);
         container->appendChild(new WrapperNode(projectFileNode));
     }

src/plugins/projectexplorer/projectnodes.cpp

@@ -908,4 +908,10 @@ ProjectNode *ContainerNode::rootProjectNode() const
     return m_project->rootProjectNode();
 }
 
+void ContainerNode::removeAllChildren()
+{
+    qDeleteAll(m_nodes);
+    m_nodes.clear();
+}
+
 } // namespace ProjectExplorer

src/plugins/projectexplorer/projectnodes.h

@@ -358,6 +358,8 @@ public:
     ProjectNode *rootProjectNode() const;
     Project *project() const { return m_project; }
 
+    void removeAllChildren();
+
 private:
     Project *m_project;
 };