Normalize number setting: Handle null, undefined, and empty string inputs

src/main.js

@@ -166,6 +166,7 @@ function clamp(value, min, max) {
 }
 
 function normalizeNumberSetting(value, fallback, { min, max, integer = false } = {}) {
+  if (value === null || value === undefined || (typeof value === 'string' && value.trim() === '')) return fallback;
   const parsed = Number(value);
   if (!Number.isFinite(parsed)) return fallback;
   const rounded = integer ? Math.trunc(parsed) : parsed;