Don't try to update if there is no print time estimate

octoprint_reservations/main.py

@@ -18,7 +18,10 @@ def get_printer_job(calendar, printer):
         print(f"Failed to get current job for {printer['name']}: {e}")
         return
 
-    if current_job["state"] == "Printing":
+    if (
+        current_job["state"] == "Printing"
+        and current_job["progress"]["printTimeLeft"] is not None
+    ):
         now = datetime.utcnow()
         start = now - timedelta(seconds=current_job["progress"]["printTime"])
         estimated_end = now + timedelta(