Fix sending empty picture when updating identity without updated picture

Closes #188

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

js/src/utils/image.ts

@@ -22,3 +22,17 @@ export function buildFileVariable<T>(file: File | null, name: string, alt?: stri
     },
   };
 }
+
+export function readFileAsync(file: File): Promise<string|ArrayBuffer|null> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+
+    reader.onload = () => {
+      resolve(reader.result);
+    };
+
+    reader.onerror = reject;
+
+    reader.readAsBinaryString(file);
+  });
+}