refactor(Stubs): convert is_null method to === null

Author: saMahmoudzadeh

stubs/Repositories/Redis/getAllBy/base.single_key_cache_strategy.stub

@@ -1,6 +1,6 @@
 $entity = $this->redisRepository->get();
 
-    if (is_null($entity)) {
+    if ($entity === null) {
         $entities = $this->repository->{{ FunctionName }}(${{ ColumnName }});
         $this->redisRepository->put($entities);
     }

stubs/Repositories/Redis/getOneBy/base.query_cache_strategy.stub

@@ -5,7 +5,7 @@ $cacheKey = $this->redisRepository->makeKey([
 
         $entity = $this->redisRepository->get($cacheKey);
 
-        if (is_null($entity)) {
+        if ($entity === null) {
             $entity = $this->repository->{{ FunctionName }}(${{ ColumnName }});
             $this->redisRepository->put($cacheKey, $entity);
         }

stubs/Repositories/Redis/getOneBy/base.single_key_cache_strategy.stub

@@ -1,6 +1,6 @@
     $entity = $this->redisRepository->get();
 
-    if (is_null($entity)) {
+    if ($entity === null) {
         $entity = $this->repository->{{ FunctionName }}(${{ ColumnName }});
         $this->redisRepository->put($entity);
     }