Fix ReferenceError by ensuring 'fn' is defined when registering shade…

…rgenerator

src/webgl/ShaderGenerator.js

@@ -1626,7 +1626,7 @@
 
 // Alias GLSL's mix function as lerp in p5.strands
 // Bridging p5.js lerp and GLSL mix for consistency in shader expressions
 const originalLerp = fn.lerp;
 fn.lerp = function (...args) {
   if (GLOBAL_SHADER?.isGenerating) {
     return fn.mix(...args); // Use mix inside p5.strands
@@ -1638,5 +1638,6 @@
 export default shadergenerator;
 
 if (typeof p5 !== 'undefined') {
-  p5.registerAddon(shadergenerator)
+  const fn = {};
+  p5.registerAddon((p5) => shadergenerator(p5, fn));
 }