use None instead of -1 for temps and wattages (#55)

* use `None` instead of `-1` for temps and wattages
this way it's easier for other tools like HomeAssistant to understand if the temperature is really negative or not available

* also handle cases where we look for `-1`

pyasic/miners/antminer/hiveon/X9/T9.py

@@ -58,7 +58,7 @@ class HiveonT9(Hiveon, T9):
             hashrate = 0
             chips = 0
             for chipset in board_map[board]:
-                if hashboard.chip_temp == -1:
+                if hashboard.chip_temp == None:
                     try:
                         hashboard.board_temp = api_stats["STATS"][1][f"temp{chipset}"]
                         hashboard.chip_temp = api_stats["STATS"][1][f"temp2_{chipset}"]