Fixed crashing for the TessieCoolingApp on main window close

Gui/QtGUIutils/QtApplication.py

@@ -1348,6 +1348,15 @@ def closeEvent(self, event):
         )
 
         if reply == QMessageBox.Yes:
+            # If running with the Tessie coldbox controller, ensure its
+            # background monitoring thread is stopped to avoid worker leaks.
+            if site_settings.cooler == "Tessie":
+                try:
+                    if hasattr(self, 'tessie_widget') and self.tessie_widget is not None:
+                        if hasattr(self.tessie_widget, 'stop_temperature_monitoring'):
+                            self.tessie_widget.stop_temperature_monitoring()
+                except Exception:
+                    logger.debug("Failed to stop Tessie monitoring cleanly during application shutdown")
             print("Application terminated")
             if self.instruments is not None:
                 self.instruments.off()

Gui/QtGUIutils/TessieCoolingApp.py

@@ -2,7 +2,7 @@
     QWidget, QPushButton, QVBoxLayout, QHBoxLayout, QGridLayout, 
     QLabel, QGroupBox, QFrame
 )
-from PyQt5.QtCore import QTimer, pyqtSignal, QThread, QObject, pyqtSlot
+from PyQt5.QtCore import QTimer, pyqtSignal, QThread, QObject, pyqtSlot,QMetaObject, Qt
 from PyQt5.QtGui import QFont
 from Gui.python.logging_config import get_logger
 import threading
@@ -241,9 +241,9 @@ def stop_temperature_monitoring(self):
         """Stop the QThread-based monitoring."""
         if self._worker is not None:
             try:
-                self._worker.stop()
-            except Exception:
-                pass
+                QMetaObject.invokeMethod(self._worker, "stop", Qt.QueuedConnection)
+            except Exception as e:
+                logger.debug(f"Failed to queue worker.stop(): {e}")
         if self._thread is not None:
             self._thread.quit()
             self._thread.wait(2000)