Fix TLV_IE_Collection.from_tlv in certain situations

The existing code used to produce an empty output in situations where a
TLV_IE_Collection would be parsed from a single TLV only with some
additional trailing padding:

>>> from pySim.utils import h2b
>>> from pySim.ts_31_102 import EF_CSGT
>>> t = EF_CSGT.Csgt_TLV_Collection()
>>> t.from_tlv(h2b('8906810300666f6fff'))
[TextCsgType(foo)]
>>> t.to_dict()
[]

This was caused by an early return (actually returning the decoded
result) but *without updating self.children*.

Change-Id: I1c84ccf698c6ff7e7f14242f9aaf7d15ac2239f4

pySim/tlv.py

@@ -361,7 +361,7 @@ class TLV_IE_Collection(metaclass=TlvCollectionMeta):
             # obtain the tag at the start of the remainder
             tag, r = first._parse_tag_raw(remainder)
             if tag == None:
-                return res
+                break
             if tag in self.members_by_tag:
                 cls = self.members_by_tag[tag]
                 # create an instance and parse accordingly