@uppy/transloadit: fix check if all files have been removed

[Murderlon]

When you use Uppy and allow uploads to start without any files added, which means you want Transloadit to import files, @uppy/transloadit currently always sends a DELETE request immediately after starting the assembly.

This is a regression from #5202

[github-actions]

Diff output files

diff --git a/packages/@uppy/transloadit/lib/index.js b/packages/@uppy/transloadit/lib/index.js
index d52478f..3ecb5db 100644
--- a/packages/@uppy/transloadit/lib/index.js
+++ b/packages/@uppy/transloadit/lib/index.js
@@ -519,7 +519,7 @@ async function _createAssembly2(fileIDs, assemblyOptions) {
       } = _ref;
       return fileIDs.includes(id);
     });
-    if (files.length === 0) {
+    if (files.length === 0 && fileIDs.length !== 0) {
       await this.client.cancelAssembly(newAssembly);
       return null;
     }