use explicit check instead of implicit checking the part for truthy a…

…s to… (#5714)

* use null check instead of implicit checking the part for truthy as to not skip part 0

* Update src/loader/playlist-loader.ts

Co-authored-by: Rob Walch <robwalch@users.noreply.github.com>

---------

Co-authored-by: Rob Walch <robwalch@users.noreply.github.com>

src/loader/playlist-loader.ts

@@ -240,7 +240,7 @@ class PlaylistLoader implements NetworkComponentAPI {
 
     // Override level/track timeout for LL-HLS requests
     // (the default of 10000ms is counter productive to blocking playlist reload requests)
-    if (context.deliveryDirectives?.part) {
+    if (Number.isFinite(context.deliveryDirectives?.part)) {
       let levelDetails: LevelDetails | undefined;
       if (
         context.type === PlaylistContextType.LEVEL &&