Coords for volume filtering aren't stored as integers, causing crash during original volume visualization

[JacobBumgarner]

Describe the bug When users load images that aren't pre-binarized, this can lead to the app crashing. Two recent users reported this issue to me.

To Reproduce Load any multi-channel image or a non-segmented image into the app.

• Multi-channel images cause crashes on loading
• Non-binary images (0 and any other single value) cause the app to crash when trying to visualize the original/smoothed volume.

Additional context To resolve this problem, I will need to halt the analysis/visualization of non-binary images and throw warnings to the user to alert them that their images aren't compatible.

[JacobBumgarner]

This problem was actually unrelated to loading non-binary images, and instead was related to the dtype of the vertex coordinate locations that were being used to slice the labeled_volume array.