linux: Disable DumpWithoutCrash() if Crashpad isn't initialized
linux: Disable DumpWithoutCrash() if Crashpad isn't initialized

When sampling has disabled crash reporting for WebView, no signal
handler is initialized, causing later calls to DumpWithoutCrash()
to crash.

Bug: 949295
Change-Id: Ib93986f81bc83404ac9f4d8f40fb34e54f1b3bec
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1558817
Reviewed-by: Mark Mentovai <f1b5a91d4d6ad523f2610114591c007e75d15084@chromium.org>
Commit-Queue: Joshua Peraza <f5809a5e35ec7e1bd0e25cb0a0b68bb433cf6f17@chromium.org>

chromium/crashpad,chromium/crashpad,chromium/crashpad