Custom cross sections can cause errors

[barrc]

The SWMM 5.1 user's manual gives the format for custom cross sections as:
Link CUSTOM Geom1 Curve (Barrels)

The new UI seems to write custom xsections that follow the user's manual.

When I run a simulation I get an error:

  ERROR 203: too few items at line 64 of [XSECT] section:
  Conduit1        	CUSTOM      	5               	3         	1         

The old UI writes custom xsections like this:

[XSECTIONS]
;;Link           Shape        Geom1            Geom2      Geom3      Geom4      Barrels    Culvert   
;;-------------- ------------ ---------------- ---------- ---------- ---------- ---------- ----------
1                CUSTOM       1                test       0          0          1                    

It seems like that SWMM might expect those 0s. I think this is the relevant SWMM code for parsing this part of the inp file

[PaulDudaRESPEC]

@barrc I've committed a fix for the issue, maybe you can verify that this indeed addresses the issue and close if appropriate.

[barrc]

@PaulDudaRESPEC this seems to fix the issue, thanks!