text: Title: crop_signal1d not updating plot
  Body: ```python
  import numpy as np
  import hyperspy.api as hs
  s = hs.signals.Signal1D(np.random.randint(0, 99, 1000))
  s.crop_signal1D() # Select a region. Press Apply
  ```
  
  The plot does not update, as seen in the image here:
  
  ![linux_crop_figure_not_updating](https://user-images.githubusercontent.com/1690979/114225537-b9f38d80-9972-11eb-85f0-2b1d018d26ab.jpg)
  
  Furthermore, pressing "OK" in the dialog box gives this error:
  
  ```python
  File "hyperspy/hyperspy/_signals/signal1d.py", line 1258, in crop_signal1D
    self.crop(axis=self.axes_manager.signal_axes[0].index_in_axes_manager,
  File "hyperspy/hyperspy/signal.py", line 2865, in crop
    i1, i2 = axis._get_index(start), axis._get_index(end)
  File "hyperspy/hyperspy/axes.py", line 340, in _get_index
    return self.value2index(value)
  File "hyperspy/hyperspy/axes.py", line 544, in value2index
    raise ValueError("The value is out of the axis limits")
  ValueError: The value is out of the axis limits
  ```
  
  Replotting the signal fixes the plotting limits.
  
  ![linux_replot_fixes_it](https://user-images.githubusercontent.com/1690979/114225560-c2e45f00-9972-11eb-8beb-6500060dc9ae.jpg)
  
  I see this in both the most recent version of RELEASE_next_patch, the conda-forge version and the newest HyperSpy bundle.