Allow users without last_activity_time

Since schema 0.0.33 User.last_activity_time is nullable and not
required. AbstractUser and its subclasses declared it as int, so a
user object without it failed with "Argument #6 ($lastActivityTime)
must be of type int, null given" and took the whole update with it.

tests/Models/UserWithPhotoTest.php

@@ -12,6 +12,23 @@ use PHPUnit\Framework\TestCase;
 #[CoversClass(UserWithPhoto::class)]
 final class UserWithPhotoTest extends TestCase
 {
+    #[Test]
+    public function optionalFieldsMayBeAbsent(): void
+    {
+        // Since schema 0.0.33 only user_id, first_name and is_bot are required
+        $user = UserWithPhoto::fromArray([
+            'user_id' => 123,
+            'first_name' => 'John',
+            'is_bot' => false,
+        ]);
+
+        $this->assertSame(123, $user->userId);
+        $this->assertNull($user->lastName);
+        $this->assertNull($user->username);
+        $this->assertNull($user->lastActivityTime);
+        $this->assertNull($user->avatarUrl);
+    }
+
     #[Test]
     public function canBeCreatedFromArray(): void
     {