test(open-banking): cover Interactive Brokers empty-statement guard

The one hook with conditional logic, emptyProviderDataMessage(), had no test: no
case fetched a valid Flex statement that parsed to zero accounts, so the 422
"No accounts found" branch was unverified and a regression there would be silent.

Add a test that fakes a successful Flex response with an empty <FlexStatements>
set and asserts the request is rejected with 422 and the NAV-section message, no
banking_connections row is created, and no warning is logged (the empty case must
not go through the credential-failure log path).

tests/Feature/OpenBanking/InteractiveBrokersControllerTest.php

@@ -6,6 +6,7 @@ use App\Models\Bank;
 use App\Models\BankingConnection;
 use App\Models\User;
 use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Log;
 use Illuminate\Support\Facades\Queue;
 use Illuminate\Support\Sleep;
 
@@ -164,3 +165,24 @@ test('reports a rate-limit message when IB throttles the request', function () {
         ->assertUnprocessable()
         ->assertJsonFragment(['message' => 'Interactive Brokers is rate limiting requests. Please wait a few minutes and try again.']);
 });
+
+test('a valid but empty flex statement returns 422 without creating a connection or logging a warning', function () {
+    Log::spy();
+
+    $user = User::factory()->onboarded()->create();
+    Http::fake([
+        '*SendRequest*' => Http::response('<FlexStatementResponse><Status>Success</Status><ReferenceCode>999</ReferenceCode></FlexStatementResponse>'),
+        '*GetStatement*' => Http::response('<FlexQueryResponse queryName="Whisper" type="AF"><FlexStatements count="0"></FlexStatements></FlexQueryResponse>'),
+    ]);
+
+    $this->actingAs($user)->postJson('/open-banking/interactive-brokers/connect', ibConnect())
+        ->assertUnprocessable()
+        ->assertJsonFragment(['message' => 'No accounts found in the Flex statement. Check that your Flex Query includes the NAV section.']);
+
+    $this->assertDatabaseMissing('banking_connections', [
+        'user_id' => $user->id,
+        'provider' => 'interactivebrokers',
+    ]);
+
+    Log::shouldNotHaveReceived('warning');
+});