Copy & Paste into other language does not set sys_language_uid
Affects: TYPO3 7.6/8.7 with up-to-date gridelements
If a grid element with children is manually copied (right click -> "copy" -> "paste" or via d&d) from a default language to another one the sys_language_uid of its children is not set correctly.
- create a grid element with one child content element in the default language
- create a translation of that page
- right click the grid element of the default language and select "Copy"
- in the translated page: Select "Paste into this column"
- the grid element is pasted into the column, but seems empty
- edit the seemingly empty grid element
- the child element was also pasted, but the value of sys_language_uid equals that of the default language