fix thread locking when reading temeprature

src/damaris/gui/DamarisGUI.py

@@ -998,8 +998,14 @@ class DamarisGUI:
         """
         # Check if temperature monitoring is enabled
         if not config.get("enable_temperature_monitoring", False):
+            # Stop any existing monitor if temperature monitoring is disabled
+            self.stop_temperature_monitoring()
             return
         
+        # Stop any existing monitor before starting a new one
+        if self.temp_monitor is not None:
+            self.stop_temperature_monitoring()
+        
         controller_type = config.get("temperature_controller_type", "eurotherm")
         temp_interval = config.get("temperature_interval", 2.0)