Fix capture threshold default reading

Author: jenshannoschwalm

src/iop/demosaic.c

@@ -383,7 +383,7 @@ int legacy_params(dt_iop_module_t *self,
     dt_iop_demosaic_params_v5_t *n = malloc(sizeof(dt_iop_demosaic_params_v5_t));
     memcpy(n, o, sizeof *o);
     n->cs_radius = 0.0f;
-    n->cs_thrs = _get_variance_threshold(self);
+    n->cs_thrs = 0.4f;
     n->cs_boost = 0.0f;
     n->cs_iter = 0;
     n->cs_center = 0.0f;

src/iop/demosaicing/capture.c

@@ -56,10 +56,10 @@ static float _get_variance_threshold(const dt_iop_module_t *self)
 
   */
   float threshold = 0.4f;
-  const dt_image_t *img = &self->dev->image_storage;
-  if(img->raw_white_point > 4096) threshold -= 0.07f;
-  if(img->exif_iso < 400)         threshold -= 0.03f;
-  if(img->exif_iso <= 100)        threshold -= 0.03f;
+  const dt_image_t *img = self->dev ? &self->dev->image_storage : NULL;
+  if(img && img->raw_white_point > 4096) threshold -= 0.07f;
+  if(img && img->exif_iso < 400)         threshold -= 0.03f;
+  if(img && img->exif_iso <= 100)        threshold -= 0.03f;
   return threshold;
 }