try try

app.py

@@ -675,7 +675,7 @@ def get_data_default(time_scale, exp):
         
     client.unsubscribe(f"pioreactor/{PIOREACTOR}/readings")
     
-    if len(temp_graph) != 0:
+    if temp_graph is not None:
         for temp in temp_graph:
             utc_time = datetime.strptime(temp["x"], "%Y-%m-%dT%H:%M:%S.%fZ")
             local_tz = pytz.timezone("America/New_York")
@@ -695,7 +695,7 @@ def get_data_default(time_scale, exp):
     else:
         plot1 = None
         
-    if len(od_graph) != 0:
+    if od_graph is not None:
         for od in od_graph:
             utc_time = datetime.strptime(od["x"], "%Y-%m-%dT%H:%M:%S.%fZ")
             local_tz = pytz.timezone("America/New_York")
@@ -715,7 +715,7 @@ def get_data_default(time_scale, exp):
     else:
         plot2 = None
     
-    if len(norm_od_graph) != 0:
+    if norm_od_graph is not None:
         for od in norm_od_graph:
             utc_time = datetime.strptime(od["x"], "%Y-%m-%dT%H:%M:%S.%fZ")
             local_tz = pytz.timezone("America/New_York")
@@ -735,7 +735,7 @@ def get_data_default(time_scale, exp):
     else:
         plot3 = None
         
-    if len(growth_rate_graph) != 0:
+    if growth_rate_graph is not None:
         for gr in growth_rate_graph:
             utc_time = datetime.strptime(gr["x"], "%Y-%m-%dT%H:%M:%S.%fZ")
             local_tz = pytz.timezone("America/New_York")