Update lights_fragment_begin.glsl.js (#27002)

Fix of 0(1578) : 'warning C7050: "geometryClearcoatNormal" might be used before being initialized' #26994 issue.

Co-authored-by: Andrew <[email protected]>

Author: c-smile

src/renderers/shaders/ShaderChunk/lights_fragment_begin.glsl.js

@@ -17,7 +17,7 @@ vec3 geometryPosition = - vViewPosition;
 vec3 geometryNormal = normal;
 vec3 geometryViewDir = ( isOrthographic ) ? vec3( 0, 0, 1 ) : normalize( vViewPosition );
 
-vec3 geometryClearcoatNormal;
+vec3 geometryClearcoatNormal = vec3( 0.0 );
 
 #ifdef USE_CLEARCOAT