surface_raster_planner_server segfaults if config is empty

[mpowelson]

If that is the case the default is supposed to get used, but we are using the wrong one. We need to take tpp_configss outside the mutex and replace this line.

const noether_msgs::ToolPathConfig& config = goal->path_configs[i];

with

const noether_msgs::ToolPathConfig& config = tpp_configs[i];

[mpowelson]

This should be beginner friendly.