Handle the case where the file reference doesn't have a path (#44410)

Summary:
The new cocoapod post install script includes aggregation and generation of privacy manifests for iOS, which is great. However, the script doesn't consider the case where the file reference doesn't have a path.

Example, for a project setup like the screenshot:
<img width="249" alt="image" src="https://github.com/facebook/react-native/assets/22592111/45dd1cf4-c2f6-4abb-940f-136a4d502966">

The code
https://github.com/facebook/react-native/blob/05a4232dd591e2d43f192d69ca14a04f4a3fb6a1/packages/react-native/scripts/cocoapods/privacy_manifest_utils.rb#L80-L81

prints `file_refs`:
```
[
<PBXFileReference name=`LaunchScreen.storyboard` path=`learnX/LaunchScreen.storyboard` UUID=`81AB9BB72411601600AC10FF`>,
<PBXVariantGroup name=`InfoPlist.strings` UUID=`D40B9F832B248EF5004BC08C`>,
<PBXFileReference path=`AppCenter-Config.plist` UUID=`D40B9F802B248EC2004BC08C`>,
<PBXFileReference name=`PrivacyInfo.xcprivacy` path=`learnX/PrivacyInfo.xcprivacy` UUID=`D403DD362BCA2BCF00E5295C`>,
<PBXFileReference name=`Assets.xcassets` path=`learnX/Assets.xcassets` UUID=`D40B9F652B248AEB004BC08C`>
]
```

where a `PBXVariantGroup` exists and it doesn't have `path`. The error `undefined method 'end_with?' for nil` occurs as a result.

## Changelog:

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[IOS] [FIXED] - In privacy manifest post install script, handle the case where the file reference doesn't have a path

Pull Request resolved: #44410

Test Plan:
1. Add a new "Strings File (Legacy)" in Xcode to the project.
2. Run `pod install` for iOS.
3. See the error `undefined method 'end_with?' for nil`.
4. Apply the fix and rerun `pod install`.
5. The script runs successfully.

Reviewed By: javache

Differential Revision: D57056159

Pulled By: cipolleschi

fbshipit-source-id: 42caaf1a98efb9111f6ff1014a5c8b7703b042f2

Author: robertying

packages/react-native/scripts/cocoapods/privacy_manifest_utils.rb

@@ -67,7 +67,7 @@ def self.read_privacyinfo_file(file_path)
     end
 
     def self.ensure_reference(file_path, user_project, target)
-        reference_exists = target.resources_build_phase.files_references.any? { |file_ref| file_ref.path.end_with? "PrivacyInfo.xcprivacy" }
+        reference_exists = target.resources_build_phase.files_references.any? { |file_ref| file_ref.path&.end_with? "PrivacyInfo.xcprivacy" }
         unless reference_exists
             # We try to find the main group, but if it doesn't exist, we default to adding the file to the project root – both work
             file_root = user_project.root_object.main_group.children.find { |group|
@@ -80,7 +80,7 @@ def self.ensure_reference(file_path, user_project, target)
 
     def self.get_privacyinfo_file_path(user_project, targets)
         file_refs = targets.flat_map { |target| target.resources_build_phase.files_references }
-        existing_file = file_refs.find { |file_ref| file_ref.path.end_with? "PrivacyInfo.xcprivacy" }
+        existing_file = file_refs.find { |file_ref| file_ref.path&.end_with? "PrivacyInfo.xcprivacy" }
         if existing_file
             return existing_file.real_path
         end