Incorrect blob_node_ids for coupling causes segmentation fault

[Jarvellis Rogers]

If the user inputs incorrect values into the parameter blob_node_ids while setting up blob-rod coupling and runs the FFEA script, it will produce a segmentation fault. For example putting in something like the following incorrect values:

<coupling type = blob-to-rod>
    <rod_id = 0>
    <blob_id = 0>
    <rod_node_id = 0>
    <blob_element_id = 0>
    <blob_node_ids = (9999999,9999999,9999999)>
    <node_weighting = (-1,-1,-1)>
    <rotation = (0,0,0)>
    <order = 0>
</coupling> 

Produces the following output after running the FFEA script (for full output see blob_id_error.log):

If possible an error message should be included to show that the incorrect node IDs were the cause.

Note that an incorrect blob_element_id does not cause this issue and will instead simply let the simulation run with the wrong parameter.