Add safe navigation to file_formats method

Why these changes are being introduced:

We are calling `uniq` on `file_formats`, which
returns a nil error if that field does not exist.

Relevant ticket(s):

- [TIMX-628](https://mitlibraries.atlassian.net/browse/TIMX-628)

How this addresses that need:

This adds a safe navigation operator to the
`file_formats` method.

Side effects of this change:

I added a regression test, which creates a new
test file. It feels a bit odd not to test the
other Record Type methods in there, but doing so
seemed far out of scope of this ticket.

Author: jazairi

app/graphql/types/record_type.rb

@@ -217,7 +217,7 @@ def publication_information
     end
 
     def file_formats
-      @object['file_formats'].uniq
+      @object['file_formats']&.uniq
     end
 
     def imprint

test/graphql/types/record_type_test.rb

@@ -0,0 +1,24 @@
+require 'test_helper'
+
+class RecordTypeTest < ActiveSupport::TestCase
+  # Test that file_formats handles nil values gracefully
+  test 'file_formats returns nil when file_formats is nil' do
+    record_data = { 'title' => 'Test Record' }
+    record_type = TimdexSchema.types['Record'].new(record_data, {})
+    
+    result = record_type.file_formats
+    assert_nil result, 'file_formats should return nil when not present in data'
+  end
+
+  # Test that file_formats works correctly when data is present
+  test 'file_formats returns unique formats when present' do
+    record_data = {
+      'title' => 'Test Record',
+      'file_formats' => ['PDF', 'PDF', 'EPUB', 'PDF']
+    }
+    record_type = TimdexSchema.types['Record'].new(record_data, {})
+    
+    result = record_type.file_formats
+    assert_equal ['PDF', 'EPUB'], result, 'file_formats should return unique values'
+  end
+end