fix: writer close if connection does not open for tcp strategy (#80)

If the asyncio.open_connection call fails, writer will never be assigned
a value, which means the comparison in the finally block will throw an
UnboundLocalError. We work around this by just assigning None to writer
at the outset

This fixes the secondary exception in #79 but not the main problem

Author: emerose

custom_components/venta/venta_strategy.py

@@ -153,6 +153,8 @@ def _build_message(
 
     async def _send_request(self, message: str) -> dict[str, Any] | None:
         """Request data from the Venta device using TCP protocol."""
+        writer = None
+
         try:
             reader, writer = await asyncio.open_connection(
                 self._host_definition.host, self._host_definition.port