Administration: Index update button remains enabled with an empty method, while the updater selection cannot be cleared

### Shopware Version

6.7.13.1

### Affected area / extension

Platform(Default)

### Actual behaviour

The selected value in the left-hand “Method” field can be cleared using the X icon. However, the “Update indexes” button remains enabled and can still be clicked even though no method is selected.

In the right-hand “Indexer and/or Updater” field, clicking the X icon does not clear the selected value.

### Expected behaviour

Button should only work, if nothing is selected at all, or in both fields something is selected.

### How to reproduce

Click x in both fields.

Start in the Administration index-update view described in the report and reproduce the issue by clearing both fields with their X icons. Trace the Method and Indexer/Updater selections and verify that the button is enabled only when both fields are selected or both are empty; confirm the fix by repeating those interactions.

Written by the indexing model from the issue text.