Test to see if logging is enabled before printing

to a log channel in StopInfoBreakpoint::PerformAction().
<rdar://problem/14651751> 

llvm-svn: 187833

lldb/source/Target/StopInfo.cpp

@@ -324,7 +324,10 @@ protected:
             if (!thread_sp->IsValid())
             {
                 // This shouldn't ever happen, but just in case, don't do more harm.
+                if (log)
+                {
                     log->Printf ("PerformAction got called with an invalid thread.");
+                }
                 m_should_stop = true;
                 m_should_stop_is_valid = true;
                 return;