Silence a warning with GCC.

miniaudio.h

@@ -49002,15 +49002,19 @@ static ma_result ma_channel_map_apply_mono_in_f32(float* pFramesOut, const ma_ch
 
                     break;  /* Get out of the switch. */
                 } else {
-                    /* Does not have left and right channels. */
+                    /* Fallthrough. Does not have left and right channels. */
+                    goto default_handler;
                 }
             } else {
-                /* Does not have stereo channels. */
+                /* Fallthrough. Does not have stereo channels. */
+                goto default_handler;
             }
         };  /* Fallthrough. See comments above. */
 
         case ma_mono_expansion_mode_duplicate:
         default:
+        {
+            default_handler:
             {
                 for (iFrame = 0; iFrame < frameCount; iFrame += 1) {
                     for (iChannelOut = 0; iChannelOut < channelsOut; iChannelOut += 1) {
@@ -49023,6 +49027,7 @@ static ma_result ma_channel_map_apply_mono_in_f32(float* pFramesOut, const ma_ch
                     pFramesOut += channelsOut;
                     pFramesIn  += 1;
                 }
+            }
         } break;
     }