Fix AttributeError in syscache plugin

[JazzCore]

dissect.ntfs changes probably caused regression in syscache plugin that now raises following AttributeError for me:

$ target-query -q -f syscache  DC1.tar
Traceback (most recent call last):
  File "/home/user/test-venv/bin/target-query", line 8, in <module>
    sys.exit(main())
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/utils.py", line 276, in wrapper
    return func(*args, **kwargs)
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/query.py", line 384, in main
    raise e
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/query.py", line 373, in main
    for record_entries in entry:
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/plugins/os/windows/syscache.py", line 78, in syscache
    full_path = self.target.fs.path("\\".join(["sysvol", mft.mft(file_segment).fullpath()]))
AttributeError: 'Mft' object has no attribute 'mft'

Also when MFT record is missing plugin raises following TypeError, PR also fixes this:

Traceback (most recent call last):
  File "/home/user/test-venv/bin/target-query", line 8, in <module>
    sys.exit(main())
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/utils.py", line 276, in wrapper
    return func(*args, **kwargs)
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/query.py", line 384, in main
    raise e
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/tools/query.py", line 373, in main
    for record_entries in entry:
  File "/home/user/test-venv/lib/python3.9/site-packages/dissect/target/plugins/os/windows/syscache.py", line 81, in syscache
    full_path = self.target.fs.path("\\".join(["sysvol", mft.ntfs.mft(file_segment).full_path()]))
TypeError: sequence item 1: expected str instance, NoneType found