Can't convert this string to number: "Medieneinladung+Knie.pdf"
The blamed expression:
==> x?number  [in template "GLOBAL.TEMPLATE.UTILS" at line 132, column 36]

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FTL stack trace ("~" means nesting-related):
	- Failed at: #assign groupId = x?number  [in template "GLOBAL.TEMPLATE.UTILS" in function "getFileEntyByArticleDocumentElement" at line 132, column 17]
	- Reached through: @fileDownload file=getFileEntyByArtic...  [in template "SRF_MEDIEN.TEMPLATE.BASE_NEWS" at line 259, column 19]
	- Reached through: #include "${templatesPath}/SRF_MEDIEN...  [in template "20115#20151#SRF_MEDIEN.TEMPLATE.INVITATION" at line 4, column 1]
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1<!-- Managed by liferay site initializer client extension --> 

2 

3<#assign hideShareButtons = true /> 

4<#include "${templatesPath}/SRF_MEDIEN.TEMPLATE.BASE_NEWS" />