Fix another getSelectedSurface() relatedbug that caused crash

src/UserInterface/ProjectionEditor.cpp

@@ -191,6 +191,7 @@ namespace ofx {
         }
         
         void ProjectionEditor::updateJoints() {
+            if (surfaceManager->getSelectedSurface()) {
                 vector<ofVec3f>& vertices =
                     surfaceManager->getSelectedSurface()->getVertices();
                 for (int i = 0; i < vertices.size(); i++) {
@@ -198,6 +199,8 @@ namespace ofx {
                 }
             }
             
+        }
+        
         void ProjectionEditor::unselectAllJoints() {
             for (int i = 0; i < joints.size(); i++) {
                 joints[i]->unselect();