No corruption alert for one line corrupted .db file on Windows with corruptAlertThreshold=0%

[nmandrescu]

On Windows:

• Datastore configured with corruptAlertThreshold=0
• replace any db file content with one line without enter (e.g. "a")
• start the app
• notice that "a" is removed and file index is recreated

Expected: DB corruption alert to be reported, since threshold is set to 0% and file content is in a bad format.

Problem source: There is an assumption that a new line always is present: https://github.com/louischatriot/nedb/blob/aa3302e5dcefa471431901a8f3fe63e532a5a7b2/lib/persistence.js#L216

Also when data.length > 0 while $$indexCreated entry is missing, this can be another sign of a corrupted DB file for a 0% threshold.