Fix many lurking undefined errors

there was an assumption that assembly is required and is never undefined
even though it is typed as optional and assigned to undefined in onError

packages/@uppy/transloadit/src/index.ts

@@ -415,6 +415,8 @@ export default class Transloadit<
         const files = this.uppy
           .getFiles()
           .filter(({ id }) => fileIDs.includes(id))
+
+          console.log(files)
         if (files.length === 0) {
           // All files have been removed, cancelling.
           await this.client.cancelAssembly(newAssembly)
@@ -603,10 +605,11 @@ export default class Transloadit<
    * When an Assembly has finished processing, get the final state
    * and emit it.
    */
-  #onAssemblyFinished(status: AssemblyResponse) {
-    const url = status.assembly_ssl_url
+  #onAssemblyFinished(assembly: Assembly) {
+    const url = assembly.status.assembly_ssl_url
     this.client.getAssemblyStatus(url).then((finalStatus) => {
-      this.assembly!.status = finalStatus
+      // eslint-disable-next-line no-param-reassign
+      assembly.status = finalStatus
       this.uppy.emit('transloadit:complete', finalStatus)
     })
   }
@@ -621,8 +624,9 @@ export default class Transloadit<
    * When all files are removed, cancel in-progress Assemblies.
    */
   #onCancelAll = async () => {
+    if (!this.assembly) return
     try {
-      await this.#cancelAssembly(this.assembly!.status)
+      await this.#cancelAssembly(this.assembly.status)
     } catch (err) {
       this.uppy.log(err)
     }
@@ -697,12 +701,13 @@ export default class Transloadit<
     // Set up the Assembly instances and AssemblyWatchers for existing Assemblies.
     const restoreAssemblies = () => {
       this.#createAssemblyWatcher(previousAssembly.assembly_id)
-      this.#connectAssembly(this.assembly!)
+      if (this.assembly == null) throw new Error('Assembly was nullish')
+      this.#connectAssembly(this.assembly)
     }
 
     // Force-update all Assemblies to check for missed events.
     const updateAssemblies = () => {
-      return this.assembly!.update()
+      return this.assembly?.update()
     }
 
     // Restore all Assembly state.
@@ -768,11 +773,11 @@ export default class Transloadit<
 
     if (this.opts.waitForEncoding) {
       assembly.on('finished', () => {
-        this.#onAssemblyFinished(assembly.status)
+        this.#onAssemblyFinished(assembly)
       })
     } else if (this.opts.waitForMetadata) {
       assembly.on('metadata', () => {
-        this.#onAssemblyFinished(assembly.status)
+        this.#onAssemblyFinished(assembly)
       })
     }
 
@@ -835,19 +840,22 @@ export default class Transloadit<
       })
     }
 
-    const assemblyID = this.assembly!.status.assembly_id
+    const assemblyID = this.assembly?.status.assembly_id
 
     const closeSocketConnections = () => {
-      this.assembly!.close()
+      this.assembly?.close()
     }
 
     // If we don't have to wait for encoding metadata or results, we can close
     // the socket immediately and finish the upload.
     if (!this.#shouldWaitAfterUpload()) {
       closeSocketConnections()
-      this.uppy.addResultData(uploadID, {
-        transloadit: [this.assembly!.status],
-      })
+      const status = this.assembly?.status
+      if (status != null) {
+        this.uppy.addResultData(uploadID, {
+          transloadit: [status],
+        })
+      }
       return Promise.resolve()
     }
 
@@ -870,9 +878,12 @@ export default class Transloadit<
 
     return this.#watcher.promise.then(() => {
       closeSocketConnections()
-      this.uppy.addResultData(uploadID, {
-        transloadit: [this.assembly!.status],
-      })
+      const status = this.assembly?.status
+      if (status != null) {
+        this.uppy.addResultData(uploadID, {
+          transloadit: [status],
+        })
+      }
     })
   }
 
@@ -982,7 +993,7 @@ export default class Transloadit<
   }
 
   getAssembly(): AssemblyResponse | undefined {
-    return this.assembly!.status
+    return this.assembly?.status
   }
 
   getAssemblyFiles(assemblyID: string): UppyFile<M, B>[] {