Fix wb_speaker_play_sound Request Message (#6843)

* fix speaker_play_sound message

* update changelog

* changelog clarification

Author: CoolSpy3

docs/reference/changelog-r2025.md

@@ -3,6 +3,7 @@
 ## Webots R2025b
   - Bug Fixes
     - Fixed a bug preventing the `webots-controller` executable from running on arm-based mac devices ([#6806](https://github.com/cyberbotics/webots/pull/6806)).
+    - Fixed a bug causing Webots to crash when multiple sounds were used with a [Speaker](speaker.md) node ([#6843](https://github.com/cyberbotics/webots/pull/6843)).
 
 ## Webots R2025a
 Released on January 31st, 2025.

src/controller/c/speaker.c

@@ -258,17 +258,17 @@ static void speaker_write_request(WbDevice *d, WbRequest *r) {
           request_write_char(r, 1);
         else
           request_write_char(r, 0);
-      }
 
-      request_write_int32(r, sound->upload_size);
-      if (sound->upload_size) {
-        /* Sound data available to stream, send it one time and discard it.
-         * Webots will cache the data inside the device.
-         */
-        request_write_data(r, sound->upload_data, sound->upload_size);
-        free(sound->upload_data);
-        sound->upload_data = NULL;
-        sound->upload_size = 0;
+        request_write_int32(r, sound->upload_size);
+        if (sound->upload_size) {
+          /* Sound data available to stream, send it one time and discard it.
+           * Webots will cache the data inside the device.
+           */
+          request_write_data(r, sound->upload_data, sound->upload_size);
+          free(sound->upload_data);
+          sound->upload_data = NULL;
+          sound->upload_size = 0;
+        }
       }
 
       sound->need_update = false;