Fix WebGL1 unit tests fail

src/Shaders/ShadersInclude/pbrBlockSheen.fx

@@ -21,7 +21,9 @@
 
     void sheenBlock(
         const in vec4 vSheenColor,
+    #ifdef SHEEN_ROUGHNESS
         const in float vSheenRoughness,
+    #endif
         const in float roughness,
     #ifdef SHEEN_TEXTURE
         const in vec2 vSheenUV,

src/Shaders/pbr.fragment.fx

@@ -244,7 +244,9 @@ void main(void) {
 
         sheenBlock(
             vSheenColor,
+        #ifdef SHEEN_ROUGHNESS
             vSheenRoughness,
+        #endif
             roughness,
         #ifdef SHEEN_TEXTURE
             vSheenUV,