mkvparser: liberalize parsing of bad elements
mkvparser: liberalize parsing of bad elements

Normally, if a sub-element of a cluster reports a size
that lies beyond the end of its enclosing cluster, we
would treat this as a malformed stream and immediately
terminate the parse.

However, if the sub-element is not a simple block or block
group, we would ignore the (sub)element anyway, so there
doesn't appear to be any harm in just concontinuing to
ignore the (sub)element, and treating this case as if
we had reached the end-of-cluster in the normal way.

Change-Id: I16c0a44f7458823ed579612d917b09ee08a8d90a

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