ui: guess WAS URL from interface IP if WAS_IP is unset

ui.py

@@ -6,6 +6,7 @@
     apply_config_host,
     apply_nvs_host,
     construct_url,
+    get_ip,
     get_nvs,
     ota,
     get_config,
@@ -93,7 +94,10 @@
     was_url = ""
     if len(user_nvs) == 0:
         try:
-            was_url = f"ws://{environ['WAS_IP']}:8502/ws"
+            if environ.get('WAS_IP') is not None:
+                was_url = f"ws://{environ['WAS_IP']}:8502/ws"
+            else:
+                was_url = f"ws://{get_ip()}:8502/ws"
             st.info("We tried to guess your WAS URL. Please make sure your Willow devices can reach this URL!")
         except Exception:
             st.info("We couldn't guess your WAS URL. Please make sure your Willow devices can reach the URL you enter!")