Fix splices at the start not being linkified

format.ts

@@ -175,7 +175,7 @@ class TextFormatter {
 
   bodyHTML(): SafeString {
     const splices = this.splices
-      .filter(({ indices }) => indices[0] && indices[1])
+      .filter(({ indices }) => indices[0] !== undefined && indices[1] !== undefined)
       .sort((a, b) => a.indices[0] - b.indices[0]);
 
     let index = 0;