ProjectExplorer: Disable copying steps to inactive kits

This fixes a hard crash due to a Target nullptr.

Change-Id: I3065ac61bc950413d8958bcad5420f5868afd35c
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/project.cpp

@@ -276,6 +276,7 @@ Target *Project::createTarget(Kit *k)
 
 bool Project::copySteps(Target *sourceTarget, Target *newTarget)
 {
+    QTC_ASSERT(newTarget, return false);
     bool fatalError = false;
     QStringList buildconfigurationError;
     QStringList deployconfigurationError;

src/plugins/projectexplorer/targetsettingspanel.cpp

@@ -447,7 +447,7 @@ public:
         });
 
         QMenu *copyMenu = menu->addMenu(tr("Copy Steps From Other Kit..."));
-        if (m_kitId.isValid()) {
+        if (m_kitId.isValid() && m_project->target(m_kitId)) {
             const QList<Kit *> kits = KitManager::kits();
             for (Kit *kit : kits) {
                 QAction *copyAction = copyMenu->addAction(kit->displayName());