Don't uninstall signal handlers if none were installed

GHC 7.8.2 calls resetSignalHandlers even when --install-signal-handlers=no is specified. On windows this results in the call to SetConsoleCtrlHandler failing.

The attached patch only calls resetSignalHandlers when there are signal handlers to remove (it mirrors the logic used when installing the handlers).

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	simonmar
Operating system
Architecture

changed weight to 5

added RTS Tbug Trac import labels

Attached file reset-sig-handlers.patch (download).

mentioned in commit bc7d49a6

changed milestone to %7.8.3

added 1 deleted label

closed

Merged, thanks!

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

removed 1 deleted label

added incorrect runtime result label

added Pnormal label