dmusic: Avoid crashing in traces if wave doesn't have a WSMPL.

dlls/dmusic/wave.c

@@ -199,6 +199,8 @@ HRESULT wave_create_from_chunk(IStream *stream, struct chunk_entry *parent, IUnk
             TRACE("    - wBitsPerSample: %u\n", This->format->wBitsPerSample);
             TRACE("    - cbSize: %u\n", This->format->cbSize);
         }
+        if (This->sample)
+        {
             TRACE(" - sample: {size: %lu, unity_note: %u, fine_tune: %d, attenuation: %ld, options: %#lx, loops: %lu}\n",
                     This->sample->head.cbSize, This->sample->head.usUnityNote,
                     This->sample->head.sFineTune, This->sample->head.lAttenuation,
@@ -208,6 +210,7 @@ HRESULT wave_create_from_chunk(IStream *stream, struct chunk_entry *parent, IUnk
                         This->sample->loops[i].cbSize, This->sample->loops[i].ulType,
                         This->sample->loops[i].ulStart, This->sample->loops[i].ulLength);
         }
+    }
 
     *ret_iface = iface;
     return S_OK;