fixup! [fix] SquashFSMountSource: Avoid resource leakage

core/ratarmountcore/SquashFSMountSource.py

@@ -534,13 +534,31 @@ def _createIndex(self) -> None:
     def __exit__(self, exception_type, exception_value, exception_traceback):
         super().__exit__(exception_type, exception_value, exception_traceback)
         self.rawFileObject.close()
-        self.image.close()
+
+        # There is no "closed" method and it can only be closed once, else we get:
+        # PySquashfsImage/__init__.py", line 131, in close
+        #     self._fd.close()
+        #     ^^^^^^^^^^^^^^
+        # AttributeError: 'NoneType' object has no attribute 'close'
+        try:
+            self.image.close()
+        except AttributeError:
+            pass
 
     def __del__(self):
         if hasattr(self, 'rawFileObject') and not self.rawFileObject.closed:
             self.rawFileObject.close()
-        if hasattr(self, 'image') and not self.image.closed:
-            self.image.close()
+
+        # There is no "closed" method and it can only be closed once, else we get:
+        # PySquashfsImage/__init__.py", line 131, in close
+        #     self._fd.close()
+        #     ^^^^^^^^^^^^^^
+        # AttributeError: 'NoneType' object has no attribute 'close'
+        try:
+            if hasattr(self, 'image'):
+                self.image.close()
+        except AttributeError:
+            pass
 
     @overrides(MountSource)
     def open(self, fileInfo: FileInfo, buffering=-1) -> IO[bytes]: