Fix lock issue with workspace dialog

CURA-4405

- Add try-except around lock release
- Fix closing the dialog with ESC

plugins/3MFReader/WorkspaceDialog.py

@@ -272,12 +272,26 @@ class WorkspaceDialog(QObject):
     def notifyClosed(self):
         self._result = {} # The result should be cleared before hide, because after it is released the main thread lock
         self._visible = False
-        self._lock.release()
+        try:
+            self._lock.release()
+        except:
+            pass
 
     def hide(self):
         self._visible = False
         self._view.hide()
-        self._lock.release()
+        try:
+            self._lock.release()
+        except:
+            pass
+
+    @pyqtSlot(bool)
+    def _onVisibilityChanged(self, visible):
+        if not visible:
+            try:
+                self._lock.release()
+            except:
+                pass
 
     @pyqtSlot()
     def onOkButtonClicked(self):
@@ -290,7 +304,6 @@ class WorkspaceDialog(QObject):
         self._view.hide()
         self.hide()
 
-
     ##  Block thread until the dialog is closed.
     def waitForClose(self):
         if self._visible: