Minor fixes for undefined values

[ChemiKyle]

I couldn't recreate either of these, but they were trivial to fix.
ef0f224 closes #71
1a4e3d2 closes #72

[Copilot]

Pull request overview

This PR fixes two minor PHP undefined value issues reported in issues #71 and #72. The first fix prevents an "Undefined constant USERID" error that occurs in certain REDCap contexts when calling getBranchingFields. The second fix prevents a "TypeError: array_keys()" error when accessing potentially undefined array keys in the project events structure.

Changes:

• Added a guard to define the USERID constant as NULL when it's not already defined, preventing errors in getBranchingFields calls
• Added null coalescing operator to safely handle potentially undefined events array structure

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[Copilot]

Inconsistent indentation: this line uses 3 spaces instead of 4 spaces like the rest of the code. The define statement should be indented with 20 spaces (or 5 levels of 4-space indentation) to align with the comment above it.

Suggested change

	define("USERID", NULL);
	define("USERID", NULL);