Migration: a zero year, month, day or OperaClass id meant the value was unknown, not that it was zero. Set to null.

Repairing character-encoding corruption (mojibake) introduced during data import; the person/ensemble name itself is unchanged. Cause: ISO-8859-1 bytes were decoded as Mac OS Roman at import (0xF6 'o-umlaut' became U+02C6, 0xE4 'a-umlaut' became U+2030). Stored value "S‰chsische Staatskapelle Dresden " is being corrected to "Sächsische Staatskapelle Dresden ". Detected by decoding the stored text back through the offending codec and confirming it yields valid UTF-8. Part of a sweep of all singers, conductors, composers, characters, operas and recordings; 419 fields matched.