Only write out the backtrace if we died from an Exception.

lib/safely/backtrace.rb

@@ -16,6 +16,7 @@ def safe_shutdown!
 
       def log_exceptions
         return unless @enabled && self.trace_directory && File.directory?( self.trace_directory )
+        return if (last_exception = $!).nil?
 
         require 'logger'
 
@@ -24,7 +25,7 @@ def log_exceptions
 
         # Log the last exception
         trace_log.info "*** Below you'll find the most recent exception thrown, this will likely (but not certainly) be the exception that made #{DaemonKit.configuration.daemon_name} exit abnormally ***"
-        trace_log.error $!
+        trace_log.error last_exception
 
         trace_log.info "*** Below you'll find all the exception objects in memory, some of them may have been thrown in your application, others may just be in memory because they are standard exceptions ***"
         ObjectSpace.each_object {|o|