When a file doesn't have a main blob, some widgets cause this error:
ERROR [DefaultActionFilter] evaluation of condition #{previewActions.hasBlobPreview(document, blobXPath)} failed: returning false javax.el.ELException: org.nuxeo.ecm.platform.preview.api.NothingToPreviewException: Can not preview a document without blob Caused by: org.nuxeo.ecm.platform.preview.api.NothingToPreviewException: Can not preview a document without blob at org.nuxeo.ecm.platform.preview.adapter.base.ConverterBasedHtmlPreviewAdapter.getBlob2preview(ConverterBasedHtmlPreviewAdapter.java:155) at org.nuxeo.ecm.platform.preview.adapter.base.ConverterBasedHtmlPreviewAdapter.getMimeType(ConverterBasedHtmlPreviewAdapter.java:92) at org.nuxeo.ecm.platform.preview.adapter.base.ConverterBasedHtmlPreviewAdapter.hasPreview(ConverterBasedHtmlPreviewAdapter.java:111) at org.nuxeo.ecm.platform.preview.helper.PreviewHelper.blobSupportsPreview(PreviewHelper.java:93) at org.nuxeo.ecm.platform.preview.seam.PreviewActionBean.hasBlobPreview(PreviewActionBean.java:173)
This is called from previewActions.hasBlobPreview in the filter view_preview evaluated by DocumentActionsBean.getBlobActions called by documentActions.getBlobActions(document, blobXPath, blob) in extended_file_widget.xhtml included by widget type extendedFile included in content_widget_template.xhtml included in widget type summary_current_document_files.