Invalid filter menu option for prefixes

[matt852]

Environment

• Nautobot version (Docker tag too if applicable): 1.5.0 (demo.nautobot.com) and on v1.5.1b1
• Python version: unknown
• Database platform, version: unknown
• Middleware(s): unknown

Steps to Reproduce

1. Go to IPAM --> Prefixes
2. Select the new Dynamic Filter box (NOT the "Max Length" filter box)
3. In the modal that pops up, on the Default tab, select ANY number for "Mask Length"
4. Click Apply

Expected Behavior

The filter should work as expected.

Observed Behavior

This error pops up for the handful of numbers I've tested this filter with:

Invalid filters were specified:
mask_length
Enter a number.

According to the UI, the filter appears to be applied but doesn't appear to be working.