nir: fix assert for wildcard pairs
nir: fix assert for wildcard pairs

The assert was null checking dest_arr_parent twice. The intention
seems to be to check both dest_ and src_.

Added in d3636da9

Reviewed-by: Eduardo Lima Mitev <86e6f0c9eba14994f25948ad50c226b324e9fa92@igalia.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler