#1490 Hotfix custom sql filter inserttags (state: open)

Description

fixes the problem with strung together and nested inserttags

this should fix https://github.com/MetaModels/core/issues/880#issuecomment-1257963684

Checklist

• Read and understood the CONTRIBUTING guidelines
• Created tests, if possible
• All tests passing
• Extended the README / documentation, if necessary
• Added myself to the @authors in touched PHP files
• Checked the changes with phpcq and introduced no new issues

@discordier workss fine for https://github.com/MetaModels/core/issues/880#issue-103936641 a) and workaround)