Don't upload file if "Use URL" is selected

## Issue
When pressing "Done", it will call the upload function, which usually results in a "please select a file" error, or the file being uploaded if a file was selected prior to switching to "Use Url".

ui/component/selectAsset/view.jsx

@@ -141,7 +141,11 @@ function SelectAsset(props: Props) {
             type="submit"
             label={useUrl ? __('Done') : __('Upload')}
             disabled={!useUrl && (uploadStatus === STATUS.UPLOADING || !pathSelected || !fileSelected)}
-            onClick={() => doUploadAsset()}
+            onClick={() => {
+              if (!useUrl) {
+                doUploadAsset();
+              }
+            }}
           />
         )}
         <FormField