fix: bug in config window when using Camera object returning None

The error image indicating that no image could be grabbed was being displayed recurrently, whereas it should only be before the very first image is captured.

Fixes #113

src/crappy/tool/camera_config/camera_config.py

@@ -112,6 +112,7 @@ def __init__(self,
     self._run = True
     self._n_loops = 0
     self._max_freq = max_freq
+    self._got_first_img: bool = False
 
     # Settings for adjusting the behavior of the zoom
     self._zoom_ratio = 0.9
@@ -1025,13 +1026,12 @@ def _update_img(self) -> None:
     ret = self._camera.get_image()
 
     # Flag raised if no image could be grabbed
-    no_img = False
+    no_img = ret is None
 
     # If no frame could be grabbed from the camera
-    if ret is None:
-      no_img = True
+    if no_img:
       # If it's the first call, generate error image to initialize the window
-      if not self._n_loops:
+      if not self._got_first_img:
         self.log(logging.WARNING, "Could not get an image from the camera, "
                                   "displaying an error image instead")
         ret = None, np.array(Image.open(BytesIO(resource_string(
@@ -1043,6 +1043,8 @@ def _update_img(self) -> None:
         sleep(0.001)
         return
 
+    # Always set, so that the error image is only ever loaded once
+    self._got_first_img = True
     self._n_loops += 1
     _, img = ret