Qbs: Simplify code a bit

Change-Id: I538f146b395d9908e0b49475ba3b5590db9e495e
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qbsprojectmanager/qbsnodes.cpp

@@ -432,11 +432,7 @@ void QbsProjectNode::update(const qbs::Project *prj)
     delete m_projectData;
     m_projectData = newData;
 
-    if (m_project) {
     delete m_project;
-        m_project = 0;
-    }
-
     m_project = prj;
 
     removeProjectNodes(toRemove);