samples: minor fixes in the tank monitoring sample

Signed-off-by: Ruben Moral <ruben.moral@digi.com>

Author: rubenmoral

samples/demos/end_to_end_tank/main.py

@@ -135,8 +135,8 @@ def read_properties():
         properties[prop] = None
 
     # Read the XBee settings saved in the firmware.
-    for prop in xbee_properties:
-        read_value = xbee.atcmd(xbee_properties[prop])
+    for prop, atcmd in xbee_properties.items():
+        read_value = xbee.atcmd(atcmd)
         if read_value is None:
             properties[prop] = None
         elif prop in text_properties:
@@ -164,7 +164,7 @@ def save_properties(properties):
     # Save XBee properties in the XBee firmware.
     for prop in xbee_properties:
         # Skip empty settings.
-        if prop not in properties or properties[prop] is None:
+        if properties.get(prop) is None:
             continue
         print("  - Saving property '%s' with '%s' in the XBee device" %
               (prop, properties[prop]))