BUG: plot_topomap slider clicking in interactive mode

[larsoner]

@drammock using the pre version appears to have shown a real bug. Not sure why it wasn't caught in non-pre runs...?

In any case I'll merge but we should try to fix this at some point.

Originally posted by @larsoner in #11781 (comment)

[larsoner]

Relevant currently-commented-out part of a test:

mne-python/mne/viz/tests/test_topomap.py

Lines 464 to 475 in 5608da2

	# TODO: Clicking the slider creates a *new* image rather than updating
	# the data directly. This makes it so that the projection is not applied
	# to the correct matplotlib Image object.
	# _fake_click(fig1, fig1.axes[1], (0.5, 0.5)) # click slider
	data_max = np.max(fig1.axes[0].images[0]._A)
	proj_fig = plt.figure(plt.get_fignums()[-1])
	assert fig1.mne.proj_checkboxes.get_status() == [False, False, False]
	pos = proj_fig.axes[0].texts[0].get_position() + np.array([0.01, 0])
	_fake_click(proj_fig, proj_fig.axes[0], pos) # toggle projector
	# make sure projector gets toggled
	assert fig1.mne.proj_checkboxes.get_status() == [True, False, False]
	assert np.max(fig1.axes[0].images[0]._A) != data_max