Fix possible ConcurrentModificationException in MimeTypeRegistry

java.util.ConcurrentModificationException: null
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043) ~[?:?]
	at java.util.ArrayList$Itr.next(ArrayList.java:997) ~[?:?]
	at org.nuxeo.ecm.platform.mimetype.service.MimetypeRegistryService.getMimetypeFromFile(MimetypeRegistryService.java:229) ~[nuxeo-core-mimetype-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.thumbnail.factories.ThumbnailDocumentFactory.getDefaultThumbnail(ThumbnailDocumentFactory.java:120) ~[nuxeo-thumbnail-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.thumbnail.factories.ThumbnailDocumentFactory.getThumbnail(ThumbnailDocumentFactory.java:69) ~[nuxeo-thumbnail-2021.45.8.jar:?]
	at org.nuxeo.ecm.core.api.thumbnail.ThumbnailServiceImpl.getThumbnail(ThumbnailServiceImpl.java:93) ~[nuxeo-core-api-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.thumbnail.rendition.ThumbnailRenditionProvider.render(ThumbnailRenditionProvider.java:45) ~[nuxeo-thumbnail-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.rendition.impl.LiveRendition.computeRenditionBlobs(LiveRendition.java:62) ~[nuxeo-platform-rendition-api-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.rendition.impl.LazyRendition.getBlobs(LazyRendition.java:60) ~[nuxeo-platform-rendition-api-2021.45.8.jar:?]
	at org.nuxeo.ecm.platform.rendition.impl.LazyRendition.getBlob(LazyRendition.java:50) ~[nuxeo-platform-rendition-api-2021.45.8.jar:?]
	at org.nuxeo.ecm.restapi.server.jaxrs.rendition.RenditionObject.getLegacyRenditionBlob(RenditionObject.java:86) ~[nuxeo-rest-api-server-2021.45.8.jar:?]