GenericKit: Fail to open if the default kit is invalid.

The generic project manager does not ask for a kit on opening a new
project, but uses the default kit.

Change-Id: I33371afb386c780ec8e3e9bbc7010ccfa4733d85
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/genericprojectmanager/genericproject.cpp

@@ -430,6 +430,9 @@ Project::RestoreResult GenericProject::fromMap(const QVariantMap &map, QString *
 
     // Sanity check: We need both a buildconfiguration and a runconfiguration!
     QList<Target *> targetList = targets();
+    if (targetList.isEmpty())
+        return RestoreResult::Error;
+
     foreach (Target *t, targetList) {
         if (!t->activeBuildConfiguration()) {
             removeTarget(t);