bug(fortran): initialises properly C ovectorstring
This is a continuation from !474 (merged)
Fixes both actions not being processed and a problem with C strings not being correctly copied into Fortran native strings.
NOTE
Using an empty string array in Fortran i.e. [""]
to set gmsh%onelab%setString
seems to be translated correctly into a empty C string and thus oes not clear the already set string. Instead, either use a space char [" "]
or a C null character [c_null_char]