Resolve false for isFilePromise if stats is undefined

Author: tsmith023

src/utils/base64.ts

@@ -9,6 +9,9 @@ const isFilePromise = (file: string | Buffer): Promise<boolean> =>
       if (err) {
         reject(err);
       }
+      if (stats == undefined) {
+        resolve(false);
+      }
       resolve(stats.isFile());
     });
   });