Temp_panel: Fix temps not updating after opening another instance

Fix #446

ks_includes/screen_panel.py

@@ -20,6 +20,7 @@ class ScreenPanel:
         self._gtk = screen.gtk
         self.control = {}
         self.title = title
+        self.devices = {}
 
         self.layout = Gtk.Layout()
         self.layout.set_size(self._screen.width, self._screen.height)

panels/temperature.py

@@ -16,7 +16,6 @@ def create_panel(*args):
 
 class TemperaturePanel(ScreenPanel):
     active_heaters = []
-    devices = {}
     graph_update = None
     active_heater = None