fix(math): add zero-range guard to map() to prevent NaN/Infinity

Author: VIPAX-JIT

src/math/calculation.js

@@ -604,6 +604,10 @@ p5.prototype.mag = function(x, y) {
  */
 p5.prototype.map = function(n, start1, stop1, start2, stop2, withinBounds) {
   p5._validateParameters('map', arguments);
+  // NEW: guard against zero input range to avoid division by zero
+  if (start1 === stop1) {
+    return start2;
+  }
   const newval = (n - start1) / (stop1 - start1) * (stop2 - start2) + start2;
   if (!withinBounds) {
     return newval;