i965: Quiet another compiler warning about uninitialized values.
i965: Quiet another compiler warning about uninitialized values.

The compiler can't tell that we're always going to hit the first if block
on the first time through the loop.

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Reviewed-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler