Correct use of -[NSString UTF8String].
Correct use of -[NSString UTF8String].

Fixes the chromium presubmit error for UTF8String:
 The use of -[NSString UTF8String] is dangerous as it can return null
 even if |canBeConvertedToEncoding:NSUTF8StringEncoding| returns YES.
 Please use |SysNSStringToUTF8| instead.

Bug: crashpad:31
Change-Id: Iaf939012ea9d342f6a01af58119cef962319aefe
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/2119613
Reviewed-by: Mark Mentovai <f1b5a91d4d6ad523f2610114591c007e75d15084@chromium.org>
Commit-Queue: Justin Cohen <45f934f548b3ee92957d72fd2179b802430e9402@chromium.org>

chromium/crashpad,chromium/crashpad,chromium/crashpad