Treat empty values from syncvalues as None

Elsewhere it's assumed that unavailable values are either not set
in state dictionary or are None. Where empty strings are used it's
logging some warnings about float conversions which aren't needed.

Author: tonyroberts

custom_components/wundasmart/pywundasmart.py

@@ -80,7 +80,8 @@ def parse_syncvalues(data: str):
     for device_state in data.splitlines():
         raw_values = device_state.split(";")
         device_values = {
-            k: urllib.parse.unquote(v) for k, v in (
+            k: (urllib.parse.unquote(v) if v else None)
+            for k, v in (
                 x.split(":") for x in raw_values if ":" in x
             )
         }
@@ -90,7 +91,7 @@ def parse_syncvalues(data: str):
         if device_sn is None:
             raise RuntimeError("No device_sn found")
 
-        hw_version = hw_version or float(device_values.get("device_hard_version", 0.0))
+        hw_version = hw_version or float(device_values.get("device_hard_version") or 0.0)
         if not hw_version:
             raise RuntimeError("No device_hard_version found")