Silence compiler warning.

Author: batt

src/libmodbus/modbus.c

@@ -497,7 +497,10 @@ int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
                 if (length_to_read != 0) {
                     step = _STEP_META;
                     break;
-                } /* else switches straight to the next step */
+                }
+                /* else switches straight to the next step */
+                /* Silence compiler warning, do not remove the following comment. */  
+                /* fall through */
             case _STEP_META:
                 length_to_read = compute_data_length_after_meta(
                     ctx, msg, msg_type);