Fix uninstalling of breakpoints when a process exits. Process

exit is still handled poorly.

R=rsc
APPROVED=rsc
DELTA=6  (6 added, 0 deleted, 0 changed)
OCL=34288
CL=34315

src/pkg/debug/proc/proc_linux.go

@@ -386,6 +386,9 @@ func (p *process) installBreakpoints() os.Error {
 //
 // Must be called from the monitor thread.
 func (p *process) uninstallBreakpoints() os.Error {
+	if len(p.threads) == 0 {
+		return nil;
+	}
 	n := 0;
 	main := p.someStoppedThread();
 	for _, b := range p.breakpoints {

usr/austin/ptrace/ptrace_linux.go

@@ -384,6 +384,9 @@ func (p *process) installBreakpoints() os.Error {
 //
 // Must be called from the monitor thread.
 func (p *process) uninstallBreakpoints() os.Error {
+	if len(p.threads) == 0 {
+		return nil;
+	}
 	n := 0;
 	main := p.someStoppedThread();
 	for _, b := range p.breakpoints {