fix: ensure_integrity_of nil guard

Add `nil` check before `.data` access; raises `FileNotFoundError` if record missing.

Author: blocknotes

lib/active_storage/service/db_service.rb

@@ -51,7 +51,7 @@ def download_chunk(key, range)
         size = range.size
         args = adapter_sqlserver? || adapter_sqlite? ? "data, #{from}, #{size}" : "data FROM #{from} FOR #{size}"
         record = object_for(key, fields: "SUBSTRING(#{args}) AS chunk")
-        raise(ActiveStorage::FileNotFoundError) unless record
+        raise ActiveStorage::FileNotFoundError unless record
 
         record.chunk
       end
@@ -160,15 +160,18 @@ def generate_url(key, expires_in:, filename:, content_type:, disposition:)
     end
 
     def ensure_integrity_of(key, checksum)
-      return if Digest::MD5.base64digest(object_for(key).data) == checksum
+      record = object_for(key)
+      raise ActiveStorage::FileNotFoundError unless record
+
+      return if Digest::MD5.base64digest(record.data) == checksum
 
       delete(key)
       raise ActiveStorage::IntegrityError
     end
 
     def retrieve_file(key)
       file = object_for(key)
-      raise(ActiveStorage::FileNotFoundError) unless file
+      raise ActiveStorage::FileNotFoundError unless file
 
       file.data
     end