fix: sections change instead of deleteing

ts/src/browser.ts

@@ -218,14 +218,17 @@ function setSectionField(si: number, key: string, val: any) {
 function setSectionType(si: number, sectionType: string) {
   const sec = getSectionByIndex(si);
   if (!sec) return;
+  const wasElementsSection = sec.sectionType !== MonoDisplay.SectionType.CustomFont;
   (sec as any).sectionType = MonoDisplay.StringToSectionType[sectionType as MonoDisplay.SectionTypeName];
   if ((sec as any).sectionType === MonoDisplay.SectionType.CustomFont) {
     (sec as any).fontData = new Uint8Array();
     delete (sec as any).elements;
     delete (sec as any).flags;
   } else {
+    if (!wasElementsSection) {
       (sec as any).elements = [];
       (sec as any).flags = {};
+    }
     delete (sec as any).fontData;
     if ((sec as any).sectionType === MonoDisplay.SectionType.ElementsTimespan) {
       const now = BigInt(Math.floor(Date.now() / 1000));