message: Fix problem if the uninitialised variable value is NaN
diff: @@ -2597,7 +2597,7 @@ void main()
  ; against the real thing when it's undefined. But we can at least expose it so that
  ; when manually checking we see the uninitialised values
  %_uninit = OpLoad %float4 %priv_float4
  - %_x = OpVectorTimesScalar %float4 %_uninit %float_0_0
  + %_x = OpExtInst %float4 %glsl450 NClamp %_uninit %float4_0000 %float4_0000
  %_out_float4 = OpFAdd %float4 %_x %float4_1234
  )EOTEST",
  R"EOTEST(
  @@ -2605,7 +2605,7 @@ void main()
  ; against the real thing when it's undefined. But we can at least expose it so that
  ; when manually checking we see the uninitialised values
  %_uninit = OpLoad %float4 %Color
  - %_x = OpVectorTimesScalar %float4 %_uninit %float_0_0
  + %_x = OpExtInst %float4 %glsl450 NClamp %_uninit %float4_0000 %float4_0000
  %_out_float4 = OpFAdd %float4 %_x %float4_1234
  )EOTEST",
  });
  