QmlDesigner: Avoiding possible regression

We have a case of a crashing puppet,
that might be related to QML2_IMPORT_PATH.
Since this only affects packages and we only see
the issue on a non developer machine, we just go back to
the old behavior for now.

Change-Id: I322cb5b02ff3b5a3dc27bab4767e6488686d216f
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/qmldesigner/designercore/instances/puppetcreator.cpp

@@ -379,7 +379,8 @@ QProcessEnvironment PuppetCreator::processEnvironment() const
     QStringList importPaths = m_model->importPaths();
     if (m_availablePuppetType == FallbackPuppet)
         importPaths.append(QLibraryInfo::location(QLibraryInfo::Qml2ImportsPath));
-    environment.appendOrSet("QML2_IMPORT_PATH", importPaths.join(pathSep), pathSep);
+    if (m_availablePuppetType != FallbackPuppet)
+        environment.appendOrSet("QML2_IMPORT_PATH", importPaths.join(pathSep), pathSep);
 
     return environment.toProcessEnvironment();
 }