fix: non-main launches no longer crash trying to shut down roscore

phyto-arm

@@ -145,6 +145,7 @@ def _start(args):
         env['ROS_LOG_DIR'] = log_dir
 
     # The following should only launch once, with the main PhytO-ARM processes
+    roscore = None
     if args.launch_name == "main":
         # Before we continue compress any older log files
         #print('Compressing older logs')
@@ -172,7 +173,7 @@ def _start(args):
     # Since we called wait() behind subprocess's back, we need to inform it that
     # the process terminated. A little hacky.
     for proc in [roscore, rosbag, nodes]:
-        if proc.pid == pid:
+        if proc is not None and proc.pid == pid:
             proc.returncode = os.WEXITSTATUS(status) \
                               if os.WIFEXITED(status) else -1