Fix TypeError in _tzicalvtz._find_comp: comp[0] should be self._comps[0]

[bysiber]

Summary

_tzicalvtz._find_comp raises TypeError when falling back to the first timezone component in an iCalendar VTIMEZONE that has no STANDARD component.

Problem

In the for...else fallback path (when no non-DST component is found), the code indexes into comp — the loop variable — rather than self._comps:

for comp in self._comps:
    if not comp.isdst:
        lastcomp = comp
        break
else:
    lastcomp = comp[0]  # TypeError: '_tzicalvtzcomp' object is not subscriptable

After the for loop completes without break, comp is the last _tzicalvtzcomp object — a plain object with no __getitem__. The intent was clearly to fall back to self._comps[0] (the first component in the list).

This is triggered when querying a datetime that falls before any transition onset in a VTIMEZONE where all components are DST (no STANDARD entry).

Fix

Replace comp[0] with self._comps[0].