TYPO3 Core

We just encountered a problem with date fields in TYPO3 v4.4.8 in an extension but it seems to be a TYPO3 related issue that is not limited to the extension.

Steps to reproduce:
- open up a record that has a datetime field with a datepicker (e.g. from pages table)
- click the datepicker to open the datepicker
- click a day in the datepicker

Expected behaviour:
- datepicker closes
- the chosen date is written into the datetime field

Current behaviour:
- datepicker closes
- nothing is written into the datetime field
- Firefox records the following error message: "oldValue is undefined" (in some compressed tceforms-[hash].js.[timestamp].gzip

Clearing all caches and deleting all the compressed JS files did not help.

The issue can be reproduced on several installations on version 4.4.8 but not on 4.5.x. For testing we downgraded to 4.4.7 where the error can't be reproduced. So we assume only 4.4.8 is affected.