[Annotations] Duplicating a new annotation not yet saved or just saved shouldn't be possible.

[pafonta]

True for all annotation types.

Case 1: Annotation not yet saved

1. Click on 'New'.
2. Enter 'Annotated text'.
3. Click on 'Localize'.
4. (Select intented match when there are several in the PDF.)
5. The button 'Duplicate' is not deactivated.

Case 2: Annotation just saved

1. Click on 'New'.
2. Enter 'Annotated text'.
3. Click on 'Localize'.
4. (Select intented match when there are several in the PDF.)
5. Click on 'Save'.
6. The button 'Duplicate' is not deactivated. Clicking on it makes NeuroCurator crashes (v0.4.4 but not v0.4.3 even if the exception is the same).

Traceback (most recent call last):
  File "/Users/fonta/repos/neurocurator/neurocurator/annotWidgets.py", line 194, in duplicateAnnotation
    self.main_window.duplicateAnnotation()
  File "/Users/fonta/repos/neurocurator/neurocurator/mainWin.py", line 1268, in duplicateAnnotation
    self.currentAnnotation = self.currentAnnotation.duplicate()
AttributeError: 'NoneType' object has no attribute 'duplicate'