Clearify unsupported export of page 0

[jonakieling]

Hi there,

EDIT: Versions are TYPO3 v9.5.31 with migration 7.8.0, did not check current LTS for this behaviour.

when exporting the page tree starting with page 0 the import fails with a misleading exception.

[ TypeError ]                                                                                                                                                
Argument 1 passed to In2code\Migration\Utility\DatabaseUtility::isFieldExistingInTable() must be of the type string, int given, called in /var/www/html/private/typo3conf/ext/migration/Classes/Port/Import.php on line 438

The reason is mal-formed entry for the page:

"pages":[[false]]

To provide some convenience for the user an exception would help to clearify that exporting page 0 or handling more than one tree at a time is not supported.

Kind regards, Jona