Added try-catch to notification close in symbol destructor (#304)

CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * [#293](https://github.com/stlehmann/pyads/pull/2939) Support WSTRINGS in structures
 
 ### Changed
+* [#304](https://github.com/stlehmann/pyads/pull/304) Implemented try-catch when closing ADS notifications in AdsSymbol destructor
 * [#292](https://github.com/stlehmann/pyads/pull/292) Improve performance of get_value_from_ctype_data for arrays
 * [#363](https://github.com/stlehmann/pyads/pull/363) Allow for platform independent builds
 

pyads/symbol.py

@@ -17,7 +17,7 @@
 
 from . import constants  # To access all constants, use package notation
 from .constants import PLCDataType
-from .pyads_ex import adsGetSymbolInfo
+from .pyads_ex import adsGetSymbolInfo, ADSError
 from .structs import NotificationAttrib
 
 # ads.Connection relies on structs.AdsSymbol (but in type hints only), so use
@@ -229,7 +229,10 @@ def __repr__(self) -> str:
 
     def __del__(self) -> None:
         """Destructor"""
-        self.clear_device_notifications()
+        try:
+            self.clear_device_notifications()
+        except ADSError:
+            pass  # Quietly continue, without a connection no cleanup could be done
 
     def add_device_notification(
             self,