i965/fs: Fix regression with SIMD8 VS since b5f1a48e234d47b24df38cb562cffb8941d43795.

i965/fs: Fix regression with SIMD8 VS since b5f1a48e234d47b24df38cb562cffb8941d43795.

With num_direct_uniforms == 0 there's no space allocated in the
param_size array for the one block of direct uniforms -- On the FS
stage this would be a harmless no-op because it would simply re-set
one of the param_size entries allocated for the sampler units to zero,
but on the VS stage it has been reported to cause memory corruption
followed by a crash -- Surprising how a full piglit run on Gen8 didn't
catch it.

Reported-and-reviewed-by: "Lofstedt, Marta" <marta.lofstedt@intel.com>