Handle empty gallery cursor when selecting media

[shai-almog]

Summary

• handle empty or null cursors returned by Android's media picker for both single and multi-selection flows
• fall back to content streams when file paths cannot be resolved and guard against null results before firing callbacks
• update helper retrieval logic to tolerate missing cursor data when resolving image paths

Testing

• not run (platform-specific change)

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https://chatgpt.com/codex/tasks/task_e_68d619c2a08483319782d443a788ebfa

[shai-almog]

Fixed #3947