Handle non-qmake projects without kits

Make it possible to add kits again after all kits were removed
from a non qmake project.

Task-number: QTCREATORBUG-7814
Change-Id: I38967cd4c106b95288b7020fe325d8cfe2688a7c
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/projectexplorer/project.cpp

@@ -439,6 +439,11 @@ void Project::configureAsExampleProject(const QStringList &platforms)
     Q_UNUSED(platforms);
 }
 
+bool Project::supportsNoTargetPanel() const
+{
+    return false;
+}
+
 void Project::onBuildDirectoryChanged()
 {
     Target *target = qobject_cast<Target *>(sender());