Update README.md with check against None

README.md

@@ -90,10 +90,11 @@ while true:
     screen_width,
     screen_height,
     context="my_context")
-
-  cursor_x, cursor_y = event.point[0], event.point[1]
-  fixation = event.fixation
-  # calibration_radius: radius for data collection during calibration
+
+  if event:
+    cursor_x, cursor_y = event.point[0], event.point[1]
+    fixation = event.fixation
+    # calibration_radius: radius for data collection during calibration
 ```
 
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@@ -132,9 +133,11 @@ event, cevent = gestures.estimate(
     screen_height,
     0, 0, 0.8, 10
 )
-cursor_x, cursor_y = event.point[0], event.point[1]
-fixation = event.fixation
-# cevent - is calibration event
+
+if event:
+  cursor_x, cursor_y = event.point[0], event.point[1]
+  fixation = event.fixation
+  # calibration_radius: radius for data collection during calibration
 ```
 
 Feel free to copy and paste the relevant code snippets for your project.