Description of problem:
noway to partition the 2nd time

Version-Release number of selected component:
anaconda-20.25.15-1

The following was filed automatically by anaconda:
anaconda 20.25.15-1 exception report
Traceback (most recent call first):
  File "/usr/lib/python2.7/site-packages/blivet/size.py", line 96, in _parseSpec
    raise SizeNotPositiveError("spec= param must be >=0")
  File "/usr/lib/python2.7/site-packages/blivet/size.py", line 164, in __new__
    self = Decimal.__new__(cls, value=_parseSpec(en_spec, False))
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/lib/disks.py", line 80, in size_str
    size = Size(en_spec="%f mb" % mb)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/lib/resize.py", line 156, in populate
    % {"freeSize": size_str(int(freeSize)), "devSize": size_str(int(dev.size))}
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/lib/resize.py", line 300, in refresh
    self.populate(disks)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/storage.py", line 919, in _show_resize_dialog
    resizeDialog.refresh(disks)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/storage.py", line 897, in on_back_clicked
    if not self._show_resize_dialog(disks):
SizeNotPositiveError: spec= param must be >=0

Additional info:
cmdline:        /usr/bin/python  /sbin/anaconda
cmdline_file:   initrd=initrd.img inst.stage2=hd:LABEL=Fedora\x2020\x20x86_64 quiet nogpt BOOT_IMAGE=vmlinuz 
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         3.11.10-301.fc20.x86_64
product:        Fedora
release:        Cannot get release name.
type:           anaconda
version:        20