A failed count no longer overwrites documentCount with null; the three callers now skip the field, and BasepullIndexStep reuses ReconcileIndexStep.safeCount instead of its own copy.
Refs #17
Both safeCount helpers (BasepullIndexStep and ReconcileIndexStep, which FullReindexStep also uses) now log a WARN with the exception and tableName before returning null, so a failing document count is visible while the run behaves as before.
Closes#17