Fix navigating between steps on start from scratch flow

inventory/src/lib/react-spreadsheet-import/src/steps/UploadFlow.tsx

@@ -213,12 +213,16 @@ export const UploadFlow = ({ state, onNext, onBack }: Props) => {
       return (
         <ValidationStepNew
           initialData={state.data} 
-          file={uploadedFile!} 
+          file={uploadedFile || new File([], "empty.xlsx")} 
           onBack={() => {
-            if (onBack) {
-              // When going back, preserve the global selections
-              setPersistedGlobalSelections(state.globalSelections)
-              onBack()
+            // If we started from scratch, we need to go back to the upload step
+            if (state.isFromScratch) {
+              onNext({
+                type: StepType.upload
+              });
+            } else if (onBack) {
+              // Use the provided onBack function
+              onBack();
             }
           }}
           onNext={(validatedData) => {
@@ -226,7 +230,7 @@ export const UploadFlow = ({ state, onNext, onBack }: Props) => {
             onNext({
               type: StepType.imageUpload,
               data: validatedData,
-              file: uploadedFile!,
+              file: uploadedFile || new File([], "empty.xlsx"),
               globalSelections: state.globalSelections
             });
           }}
@@ -238,21 +242,13 @@ export const UploadFlow = ({ state, onNext, onBack }: Props) => {
         <ImageUploadStep
           data={state.data}
           file={state.file}
-          onBack={() => {
-            if (onBack) {
-              onNext({
-                type: StepType.validateData,
-                data: state.data,
-                globalSelections: state.globalSelections
-              })
-            }
-          }}
+          onBack={onBack}
           onSubmit={(data, file) => {
             // Create a Result object from the array data
             const result = {
-              validData: data,
-              invalidData: [],
-              all: data
+              validData: data as Data<string>[],
+              invalidData: [] as Data<string>[],
+              all: data as Data<string>[]
             };
             onSubmit(result, file);
           }}