Fix: EEVEE: Fix crash on start

Add missing function pre-declaration.
Partially fixes issue ##116964.
(Render no longer crashes, but shading is broken)

source/blender/draw/engines/eevee/shaders/closure_type_lib.glsl

@@ -67,6 +67,7 @@ Closure closure_eval(ClosureHair hair);
 Closure closure_eval(ClosureReflection reflection, ClosureRefraction refraction);
 /* Dielectric BSDF. */
 Closure closure_eval(ClosureDiffuse diffuse, ClosureReflection reflection);
+Closure closure_eval(ClosureSubsurface diffuse, ClosureReflection reflection);
 /* Coat BSDF. */
 Closure closure_eval(ClosureReflection reflection, ClosureReflection coat);
 /* Volume BSDF. */