filesystem: Don't pass empty string to parse_select_response()

This happens e.g. when selecting the ARA-M applet on sysmoISIM-SJA2:

pySIM-shell (MF)> select ADF.ARA-M
-> 00a4040409 a00000015141434c00
<- 9000:
Traceback (most recent call last):
  File "/space/home/laforge/.local/lib/python3.9/site-packages/cmd2/cmd2.py", line 2064, in onecmd_plus_hooks
    stop = self.onecmd(statement, add_to_history=add_to_history)
  File "/space/home/laforge/.local/lib/python3.9/site-packages/cmd2/cmd2.py", line 2494, in onecmd
    stop = func(statement)
  File "/space/home/laforge/projects/git/pysim/./pySim-shell.py", line 750, in do_select
    fcp_dec = self._cmd.rs.select(path, self._cmd)
  File "/space/home/laforge/projects/git/pysim/pySim/filesystem.py", line 1314, in select
    select_resp = f.decode_select_response(data)
  File "/space/home/laforge/projects/git/pysim/pySim/filesystem.py", line 193, in decode_select_response
    return self.parent.decode_select_response(data_hex)
  File "/space/home/laforge/projects/git/pysim/pySim/filesystem.py", line 378, in decode_select_response
    return profile.decode_select_response(data_hex)
  File "/space/home/laforge/projects/git/pysim/pySim/ts_102_221.py", line 796, in decode_select_response
    t.from_tlv(h2b(resp_hex))
  File "/space/home/laforge/projects/git/pysim/pySim/tlv.py", line 231, in from_tlv
    (rawtag, remainder) = self.__class__._parse_tag_raw(do)
  File "/space/home/laforge/projects/git/pysim/pySim/tlv.py", line 258, in _parse_tag_raw
    return bertlv_parse_tag_raw(do)
  File "/space/home/laforge/projects/git/pysim/pySim/utils.py", line 208, in bertlv_parse_tag_raw
    if binary[0] == 0xff and len(binary) == 1 or binary[0] == 0xff and binary[1] == 0xff:
IndexError: bytearray index out of range
EXCEPTION of type 'IndexError' occurred with message: 'bytearray index out of range'

Change-Id: I910e6deba27d1483dff1e986c89f1a1b2165f49b

pySim/filesystem.py

@@ -363,7 +363,7 @@ class CardMF(CardDF):
                 {x.name: x for x in self.applications.values() if x.name})
         return sels
 
-    def decode_select_response(self, data_hex: str) -> object:
+    def decode_select_response(self, data_hex: Optional[str]) -> object:
         """Decode the response to a SELECT command.
 
         This is the fall-back method which automatically defers to the standard decoding
@@ -372,6 +372,9 @@ class CardMF(CardDF):
         install specific decoding.
         """
 
+        if not data_hex:
+            return data_hex
+
         profile = self.get_profile()
 
         if profile: