Description of problem:
Blivet partitioning crashed on Fedora-Everything-netinst-x86_64-33_Beta-1.3.iso. I created a BIOS boot partition smaller than I wanted, so I tried to resize it. I was testing bug 1881472 and I had the updates.img from bug 1881472 comment 20 applied.

Reproducer:
1. enter Blivet part with a clean disk
2. click Add partition
3. select BIOS boot, make it 1024kB
4. confirm
5. decide you want to make it 2MB
6. right click on the pending biosboot partition (vda1 in my case)
7. select Edit->Resize
8. crash

Version-Release number of selected component:
anaconda-33.25.2

The following was filed automatically by anaconda:
anaconda 33.25.2 exception report
Traceback (most recent call first):
  File "/usr/lib/python3.9/site-packages/blivetgui/communication/client.py", line 176, in remote_call
    raise type(ret.exception)(str(ret.exception) + "\n" + ret.traceback)  # pylint: disable=maybe-no-member
  File "/usr/lib/python3.9/site-packages/blivetgui/blivetgui.py", line 282, in resize_device
    self.client.remote_call("device_resizable", device))
AttributeError: 'BlivetStorageHandler' object has no attribute '_resizable_filesystems'
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/blivetgui/communication/server.py", line 317, in _call_utils_method
    ret = utils_method(*args)
  File "/usr/lib/python3.9/site-packages/blivetgui/blivet_utils.py", line 636, in device_resizable
    elif blivet_device.format.type not in self.resizable_filesystems:
  File "/usr/lib/python3.9/site-packages/blivetgui/blivet_utils.py", line 169, in resizable_filesystems
    if self._resizable_filesystems is None:
AttributeError: 'BlivetStorageHandler' object has no attribute '_resizable_filesystems'


Additional info:
addons:         com_redhat_kdump
cmdline:        /usr/bin/python3  /sbin/anaconda
cmdline_file:   BOOT_IMAGE=vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=Fedora-E-dvd-x86_64-33 quiet inst.updates=https://vtrefny.fedorapeople.org/img/rhbz1881472.img
executable:     /sbin/anaconda
hashmarkername: anaconda
hawkey.log:     INFO Sep-23 12:17:12 === Started libdnf-0.48.0 ===
kernel:         5.8.6-301.fc33.x86_64
product:        Fedora
release:        Fedora release 33 (Thirty Three)
release_type:   pre-release
type:           anaconda
version:        33