Add atError when kz=0 in gwig.c

[SebastienJoly]

I added some safeguards in the gwig.c integrator following the discussion in: #1075
It raises an atError whenever a wiggler with kz=0 (in By or Bx) is called.

I am not sure whether I should call check_error() after atError(). What would you recommend?

[swhite2401]

Ok!

[lfarv]

Unfortunately, your test is done after the element structure is allocated, and so it creates a memory leak: the structure will never be released. It should be moved inside trackFunction (see #1075 (comment)) and executed before the line

Elem = (struct elem*)atMalloc(sizeof(struct elem));

and with a check_error().

(Sorry, I had no time to review yesterday…)

[swhite2401]

Oups I missed that...I went to fast on that one.... thanks @lfarv!