fixed submitting form

frontend/src/pages/MainForm.tsx

@@ -204,16 +204,9 @@ export const MainForm = () => {
         <FormControlLabel control={<Checkbox />} label={t("transfer")} />
         <TextField required id="code" label={t("code")} variant="filled" />
         {isLoading && <CircularProgress />}
-        <button type="submit">
-          <Button
-            onClick={() => {
-              handleSubmit();
-            }}
-            variant="contained"
-          >
-            {t("submit")}
-          </Button>
-        </button>
+        <Button type="submit" variant="contained" disabled={isLoading}>
+          {t("submit")}
+        </Button>
 
         {msg && (
           <Alert severity={msg.type}>