fix: handle undefined id in heading insertion check

[wendyyuchensun]

Summary

Fixes a crash when inserting images through the upload modal by adding optional chaining to handle cases where insertLatex is called without an id property.

Problem

The insertLatex function in home.js:170 attempted to call .startsWith('heading') on an id that could be undefined, causing a runtime error and crashing the application when inserting images.

Root cause: The image upload handler calls insertLatex without providing an id property:

Access8MathWeb/src/components/edit-icons-tab.js

Lines 31 to 34 in 922247c

	insertLatex({
	latex: ``,
	offset: -1,
	});

When insertLatex attempts to check if id.startsWith('heading'), it throws: TypeError: Cannot read property 'startsWith' of undefined.

Solution

1. Added optional chaining operator (?.) to safely check if id exists before calling .startsWith().
2. Added id: 'insert_image_file' to the insertLatex call in the image upload handler to provide a proper identifier for image insertion operations.