RT crashes when viewing Nikon D1X files with demosaicer set to 'None' and hovering about the right or lower part of the image, fixes #4436

rtengine/rawimagesource.cc

@@ -5349,6 +5349,10 @@ void RawImageSource::init ()
 
 void RawImageSource::getRawValues(int x, int y, int rotate, int &R, int &G, int &B)
 {
+    if(d1x) { // Nikon D1x has special sensor. We just skip it
+        R = G = B = 0;
+        return;
+    }
     int xnew = x + border;
     int ynew = y + border;
     rotate += ri->get_rotateDegree();