Call read() if there is any existing in-flight request

This fixes the downloader getting stuck if there's a particularly large
file, such that we've read all the current inbound data but haven't sent
a new request yet as we still have 200 in-flight.

Signed-off-by: Graham <gpe@openrs2.org>

archive/src/main/kotlin/org/openrs2/archive/cache/Js5ChannelHandler.kt

@@ -71,6 +71,9 @@ public class Js5ChannelHandler(
 
         if (flush) {
             ctx.flush()
+        }
+
+        if (inFlightRequests.isNotEmpty()) {
             ctx.read()
         }
     }