perform render thumbnail only if framebuffer available

RenderView.cpp

@@ -76,16 +76,11 @@ void RenderView::draw()
         scene.root()->draw(glm::identity<glm::mat4>(), P);
         fading_overlay_->draw(glm::identity<glm::mat4>(), projection);
         frame_buffer_->end();
-    }
 
         // if a thumbnailer is pending
         if (thumbnailer_.size() > 0) {
 
             try {
-            // promise will fail if no framebuffer
-            if ( frame_buffer_ == nullptr )
-                throw std::runtime_error("no frame");
-
                 // new thumbnailing framebuffer
                 FrameBuffer *frame_thumbnail = new FrameBuffer( glm::vec3(SESSION_THUMBNAIL_HEIGHT * frame_buffer_->aspectRatio(), SESSION_THUMBNAIL_HEIGHT, 1.f) );
 
@@ -116,7 +111,7 @@ void RenderView::draw()
             // done with this promise
             thumbnailer_.pop_back();
         }
-
+    }
 }
 
 
@@ -136,7 +131,8 @@ FrameBufferImage *RenderView::thumbnail ()
         img = t.get();
     }
     // catch any failed promise
-    catch (std::runtime_error&){  }
+    catch (std::runtime_error&){
+    }
 
     return img;
 }