Use the default server download protocol if spaces are not supported

changelog/unreleased/thumbnails-download-fix.md

@@ -0,0 +1,3 @@
+Bugfix: Use the default server download protocol if spaces are not supported
+
+https://github.com/owncloud/ocis/pull/3386

thumbnails/pkg/thumbnail/imgsource/cs3.go

@@ -74,8 +74,12 @@ func (s CS3) Get(ctx context.Context, path string) (io.ReadCloser, error) {
 	for _, p := range rsp.Protocols {
 		if p.Protocol == "spaces" {
 			ep, tk = p.DownloadEndpoint, p.Token
+			break
 		}
 	}
+	if (ep == "" || tk == "") && len(rsp.Protocols) > 0 {
+		ep, tk = rsp.Protocols[0].DownloadEndpoint, rsp.Protocols[0].Token
+	}
 
 	httpReq, err := rhttp.NewRequest(ctx, "GET", ep, nil)
 	if err != nil {