TYPO3 Core

Adding a new content element to a already translated gridelement in the default language and then clicking the translate button causes an empty summary of content uids, which leads to an error at the finishing step.

How to reproduce:
- TYPO3 9 Site Setup with multiple languages.
- Install gridelements extension.
- Create a grid container.
- Click on translate and select translate or copy.
- Now create a new content element inside of the grid container in the default language.
- Click again on translate.
- The new content element is missing in step 3.
- The final step can not be finished and you need to exit with ESC.

Current workaround:
We could figure out that the problem is related to the special colPos value of the content in grid container: -1.
This value is ignored and the content element is not found.
Adding a pseudo-column in the backend-layout with the colPos -1 fixes the issue.

Furthermore we found the loop of the columnUids in Build/Sources/TypeScript/backend/Resources/Public/TypeScript/Localization.ts

Line 180: columnList.forEach((colPos: number): void => {
...

All the content in the column -1 is ignored, because the value is not in the columnList.
Possible fix would be adding "-1" to the columnList.