[scudo] releaseToOSMaybe can fail if it can't allocate PageMap

PageMap is allocated with MAP_ALLOWNOMEM if there's no static buffer
left. So it can be failed and return nullptr without any assertion
triggered. Instead of crashing in the releaseToOSMaybe in the middle,
just return and let the program handles the page failure.

Reviewed By: cferris

Differential Revision: https://reviews.llvm.org/D151379

Bug: 283931461
Bug: 284324891

GitOrigin-RevId: 11ea40cff5413057d823a4b3ac5ac419b674dc56
Change-Id: I9b83dc3cfdda9a64456a223f3f5a43d6faa461bc
Merged-In: I9b83dc3cfdda9a64456a223f3f5a43d6faa461bc
(cherry picked from commit b140c322ca8d4732b2b6314fa8b0a8a98d253950)