let get_selection_account return an Option<>

deltachat-ffi/deltachat.h

@@ -2486,6 +2486,7 @@ dc_context_t*  dc_accounts_get_account          (dc_accounts_t* accounts, uint32
  *     unmanaged account-context as created by dc_context_new().
  *     Once you do no longer need the context-object, you have to call dc_context_unref() on it,
  *     which, however, will not close the account but only decrease a reference counter.
+ *     If there is no selected account, NULL is returned.
  */
 dc_context_t*  dc_accounts_get_selected_account (dc_accounts_t* accounts);
 

deltachat-ffi/src/lib.rs

@@ -3695,8 +3695,9 @@ pub unsafe extern "C" fn dc_accounts_get_selected_account(
     }
 
     let accounts = &*accounts;
-    let ctx = block_on(accounts.get_selected_account());
-    Box::into_raw(Box::new(ctx))
+    block_on(accounts.get_selected_account())
+        .map(|ctx| Box::into_raw(Box::new(ctx)))
+        .unwrap_or_else(std::ptr::null_mut)
 }
 
 #[no_mangle]