Fix bounds checking error when parsing WWW-Authenticate field

[toffaletti]

Without the fix:

swift test --filter TestURLProtectionSpace.test_createWithInvalidAuth
Test Suite 'Selected tests' started at 2024-10-11 21:04:24.085
Test Suite 'TestURLProtectionSpace' started at 2024-10-11 21:04:24.095
Test Case 'TestURLProtectionSpace.test_createWithInvalidAuth' started at 2024-10-11 21:04:24.095
Swift/StringIndexValidation.swift:143: Fatal error: Substring index is out of bounds

^C*** Signal 5: Backtracing from 0xffff95642744... failed ***

With the fix:

Test Suite 'Selected tests' started at 2024-10-11 21:19:30.602
Test Suite 'TestURLProtectionSpace' started at 2024-10-11 21:19:30.612
Test Case 'TestURLProtectionSpace.test_createWithInvalidAuth' started at 2024-10-11 21:19:30.612
Test Case 'TestURLProtectionSpace.test_createWithInvalidAuth' passed (0.005 seconds)
Test Suite 'TestURLProtectionSpace' passed at 2024-10-11 21:19:30.617
	 Executed 1 test, with 0 failures (0 unexpected) in 0.005 (0.005) seconds
Test Suite 'Selected tests' passed at 2024-10-11 21:19:30.617
	 Executed 1 test, with 0 failures (0 unexpected) in 0.005 (0.005) seconds

[jrflat]

Thanks!

[jrflat]

@swift-ci please test

[toffaletti]

CI failure seems unrelated to my changes.

/Users/ec2-user/jenkins/workspace/swift-corelibs-foundation-PR-macOS/branch-main/swift-corelibs-xctest/Sources/XCTest/Public/XCTestMain.swift:21:23: error: no such module 'SwiftFoundation'
    @_exported import SwiftFoundation
                      ^

note: Using global toolchain override 'Xcode Default'. (in target 'SwiftXCTest' from project 'XCTest')
** BUILD FAILED **


The following build commands failed:
	CompileSwift normal arm64 (in target 'SwiftXCTest' from project 'XCTest')
	SwiftCompile normal arm64 Compiling\ XCTestObservationCenter.swift,\ IgnoredErrors.swift,\

[parkera]

@shahmishal can we get macOS CI turned off on this repo? We don’t build swift-corelibs-foundation for macOS

[jrflat]

Agree macOS failure looks unrelated, not unique to this PR