I don't know the gsl library, but it seems to me than you're not initializing properly the complex numbers before adding into the array ... :
Complex numbers are represented using the type gsl_complex. The internal representation of this type may vary across platforms and should not be accessed directly. The functions and macros described below allow complex numbers to be manipulated in a portable way.
For reference, the default form of the gsl_complex type is given by the following struct,