Return NaN from int() for unrecognised input types

[Chessing234]

Bug

p5.prototype.int() silently returns undefined when it's given a
value that doesn't match any of its recognised input types, so callers
that pass null, undefined, or a plain object get a non-numeric
result that poisons downstream arithmetic (e.g. int(null) + 1 is
NaN, but from an unexpected source — the debugger shows int()
returned undefined, not a number).

Root cause

p5.prototype.int = function(n, radix = 10) {
  if (n === Infinity || n === 'Infinity') {
    return Infinity;
  } else if (n === -Infinity || n === '-Infinity') {
    return -Infinity;
  } else if (typeof n === 'string') {
    return parseInt(n, radix);
  } else if (typeof n === 'number') {
    return n | 0;
  } else if (typeof n === 'boolean') {
    return n ? 1 : 0;
  } else if (n instanceof Array) {
    return n.map(n => p5.prototype.int(n, radix));
  }
};

Every branch returns a concrete value, but the if/else if chain has
no final else, so unmatched types fall off the end and JavaScript
returns undefined implicitly.

Why the fix is correct

• Matches the documented behaviour of the sibling float() helper in
  the same file, whose docstring already promises:
  "If a string can't be converted to a number, as in float('giraffe'),
  then the value NaN (not a number) will be returned."
• NaN is the conventional JavaScript signal for "couldn't coerce
  to a number" (same as what parseInt/Number produce for bad
  input), so downstream math produces NaN in a predictable,
  self-describing way instead of a silent undefined.
• Every existing code path is untouched; the new return NaN; only
  runs on inputs that previously fell through to undefined.

Change

src/utilities/conversion.js: add return NaN; at the end of
p5.prototype.int. One-line addition.

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Thank You!

[ksen0]

This does not link to an open bug report, so I will close it. Please review contribution guidelines before making future PRs. Thank you!

[alialobidm]

`` #8645