Merge branch 'offset-crosshair' of https://github.com/TheDeanLab/navigate into offset-crosshair

Author: AdvancedImagingUTSW

src/navigate/controller/sub_controllers/camera_view.py

@@ -883,6 +883,8 @@ def process_image(self):
         image intensity, adds a crosshair, applies the lookup table, and populates the
         image.
         """
+        if self.image is None:
+            return
         image = self.digital_zoom()
         self.detect_saturation(image)
         image = self.down_sample_image(image)