fix: null-safe json_decode in RedisDriver; add getSessionModel test to MultiDriverTest

src/Drivers/RedisDriver.php

@@ -57,7 +57,7 @@ public function getItems(): array
     {
         $data = $this->redis->connection($this->connection)->get($this->itemsKey());
 
-        return $data ? json_decode($data, true) : [];
+        return $data ? (json_decode($data, true) ?? []) : [];
     }
 
     public function putItems(array $items): void
@@ -73,7 +73,7 @@ public function getConditions(): array
     {
         $data = $this->redis->connection($this->connection)->get($this->conditionsKey());
 
-        return $data ? json_decode($data, true) : [];
+        return $data ? (json_decode($data, true) ?? []) : [];
     }
 
     public function putConditions(array $conditions): void

tests/Unit/Drivers/MultiDriverTest.php

@@ -77,4 +77,8 @@
     test('throws when constructed with no drivers', function () {
         expect(fn() => new MultiDriver([]))->toThrow(InvalidArgumentException::class);
     });
+
+    test('getSessionModel delegates to primary driver', function () {
+        expect($this->driver->getSessionModel())->toBeNull();
+    });
 });