Segfault closing second detail window before its done rendering, Issue 2395

rtengine/improccoordinator.h

@@ -205,6 +205,9 @@ class ImProcCoordinator : public StagedImageProcessor {
         void getSpotWB   (int x, int y, int rectSize, double& temp, double& green);
         void getAutoCrop (double ratio, int &x, int &y, int &w, int &h);
 
+        bool updateTryLock () {return updaterThreadStart.trylock();}
+        void updateUnLock () {updaterThreadStart.unlock();}
+
         void setProgressListener (ProgressListener* pl)  { plistener = pl; }
         void setPreviewImageListener    (PreviewImageListener* il)     {imageListener = il; }
         void setSizeListener     (SizeListener* il)      {sizeListeners.push_back (il); }

rtengine/rtengine.h

@@ -330,6 +330,10 @@ namespace rtengine {
               * @return the height of the preview image */
             virtual int         getPreviewHeight () =0;
 
+			virtual bool		updateTryLock() = 0;
+
+			virtual void		updateUnLock() = 0;
+
             /** Creates and returns a Crop instance that acts as a window on the image
               * @param editDataProvider pointer to the EditDataProvider that communicates with the EditSubscriber
               * @return a pointer to the Crop object that handles the image data trough its own pipeline */