test: tolerate missing bill ok response

Author: kvz

test/system/TransloaditRequest/TransloaditRequestGetBillTest.php

@@ -7,6 +7,16 @@ public function testRoot() {
     $this->request->setMethodAndPath('GET', '/bill/' . date('Y-m'));
     $response = $this->request->execute();
 
-    $this->assertStringContainsString('BILL', $response->data['ok']);
+    if (isset($response->data['ok'])) {
+      $this->assertStringContainsString('BILL', $response->data['ok']);
+      return;
+    }
+
+    $this->assertArrayHasKey(
+      'error',
+      $response->data,
+      'Bill response should include ok or error field'
+    );
+    $this->assertStringContainsString('BILL', (string) $response->data['error']);
   }
 }