prevent file data loss due to replacing an open file handle (partial fix for #5275)

[softhack007]

The function writeObjectToFile() was re-assigning f (global file handle, file.cpp) without first completing any pending write operations on f.

Reassigning a file pointer thats still in use can lead to loss of data and file corruption.
This PR provides a fix by first checking for pending writes (doCloseFile == true) and calling f.close() when needed.

The same protection code is already preset in readObjectFromFile(), it looks like protecting writeObjectToFile() was forgotten.

Summary by CodeRabbit

• Bug Fixes
  • Improved file-handling reliability by ensuring files are properly closed when needed.
  • Ensured cached file data is flushed before files are reopened or written, reducing risk of data loss and improving consistency.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

Calls to closeFile() unchanged; an explanatory comment clarifies internal null-check is inside f.close(). writeObjectToFile() now invokes closeFile() before reopening when doCloseFile is set to ensure any cached data is flushed.

Changes

Cohort / File(s)	Summary
File I/O guard and flush behavior wled00/file.cpp	closeFile() left functionally unchanged with added explanatory comment about internal null-check; writeObjectToFile() now performs a pre-close by calling closeFile() when doCloseFile is true to flush cached data before reopening the file.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding a safeguard to prevent file data loss when replacing an open file handle in writeObjectToFile(), which directly matches the PR objectives.

✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 8e27fe4 and a870474.

📒 Files selected for processing (1)

• wled00/file.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

• wled00/file.cpp

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