Missing null check in DefaultModelValidator.validateProfileId() can cause NPE

[abhu85]

Affected version

4.1.0-SNAPSHOT (master)

Bug description

In impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelValidator.java, the validateProfileId() method is missing a null check before calling validProfileIds.contains(id).

Since validProfileIds is a ConcurrentHashMap.newKeySet() (which doesn't allow null keys), passing a null profile ID will throw a NullPointerException instead of a proper validation error.

Inconsistency:

The same file has two similar validation methods with inconsistent null handling:

// Line ~1743 - HAS null check (correct)
private boolean validateCoordinateId(..., String id, ...) {
    if (id != null && validCoordinatesIds.contains(id)) {
        return true;
    }
    // ...
}

// Line ~1794 - MISSING null check (bug)
private boolean validateProfileId(..., String id, ...) {
    if (validProfileIds.contains(id)) {  // Will throw NPE if id is null
        return true;
    }
    // ...
}

Expected behavior

validateProfileId() should handle null IDs gracefully by either:

1. Adding a null check like validateCoordinateId() does: if (id != null && validProfileIds.contains(id))
2. Or letting the subsequent validation report the proper error message

Steps to reproduce

1. Create a POM with a profile that has a null/missing ID
2. Run validation with Maven 4
3. Observe NPE instead of proper validation error

Proposed fix

// Change from:
if (validProfileIds.contains(id)) {

// To:
if (id != null && validProfileIds.contains(id)) {

This makes it consistent with validateCoordinateId() and the compat module fix in #11739.

---

Discovered during code review of #11739