fix: DBNMQTTool — 所有 publish 路径增加通用异常捕获

问题: _custom_publish / _proto_publish / _sim_publish 只 catch
json.JSONDecodeError, MqttClient.publish() 抛出的 ConnectionError
等异常未被捕获, 在 Qt 信号槽中导致静默崩溃(Windows 无 traceback).

修复:
- _custom_publish: +except Exception, 避免 toPlainText() 重复调用
- _proto_publish: +except Exception, 避免 toPlainText() 重复调用
- _sim_publish: +except Exception
- _custom_subscribe/_custom_unsubscribe: +except Exception, +_client 空检查

DBNMQTTool/main.py

@@ -453,6 +453,8 @@ class MainWindow(QMainWindow):
             self._log(f"[模拟] → {topic}")
         except json.JSONDecodeError as e:
             QMessageBox.warning(self, "JSON 错误", str(e))
+        except Exception as e:
+            QMessageBox.critical(self, "发布失败", f"{type(e).__name__}: {e}")
 
     def _sim_send_loop(self):
         sn = self._sim_sn.text()
@@ -576,15 +578,18 @@ class MainWindow(QMainWindow):
         if not topic or not self._mqtt.connected:
             QMessageBox.warning(self, "提示", "请输入 Topic 并连接 Broker")
             return
+        raw = self._proto_payload.toPlainText().strip()
         try:
-            if self._proto_payload.toPlainText().strip():
+            if raw:
-                payload = json.loads(self._proto_payload.toPlainText())
+                payload = json.loads(raw)
             else:
                 payload = build_request(CMD_DEV_INFO_QUERY)
             self._mqtt.publish(topic, payload)
             self._log(f"[协议] → {topic}")
         except json.JSONDecodeError as e:
             QMessageBox.warning(self, "JSON 错误", str(e))
+        except Exception as e:
+            QMessageBox.critical(self, "发布失败", f"{type(e).__name__}: {e}")
 
     # ================================================================
     # 自定义 Topic 订阅/发布
@@ -677,21 +682,26 @@ class MainWindow(QMainWindow):
         topic = self._custom_pub_topic.text()
         if not topic:
             return
+        raw = self._custom_payload.toPlainText().strip()
         try:
-            payload = json.loads(self._custom_payload.toPlainText()) if self._custom_payload.toPlainText().strip() else {}
+            payload = json.loads(raw) if raw else {}
             qos = int(self._custom_qos.currentText())
             self._mqtt.publish(topic, payload, qos=qos)
             self._log(f"[自定义] → {topic}")
         except json.JSONDecodeError as e:
             QMessageBox.warning(self, "JSON 错误", str(e))
+        except Exception as e:
+            QMessageBox.critical(self, "发布失败", f"{type(e).__name__}: {e}")
+            self._log(f"[自定义] 发布失败: {e}")
 
     def _custom_subscribe(self):
-        if not self._mqtt.connected:
+        if not self._mqtt.connected or not self._mqtt._client:
             QMessageBox.warning(self, "提示", "请先连接 Broker")
             return
         topic = self._custom_sub_topic.text()
         if not topic:
             return
+        try:
             qos = int(self._custom_sub_qos.currentText())
             self._mqtt._client.subscribe(topic, qos=qos)
             self._custom_subs[topic] = qos
@@ -706,19 +716,27 @@ class MainWindow(QMainWindow):
             if not found:
                 self._custom_sub_list.addTopLevelItem(QTreeWidgetItem([topic, str(qos)]))
             self._log(f"[订阅] {topic} (QoS={qos})")
+        except Exception as e:
+            QMessageBox.critical(self, "订阅失败", f"{type(e).__name__}: {e}")
+            self._log(f"[订阅] 失败: {e}")
 
     def _custom_unsubscribe(self):
         items = self._custom_sub_list.selectedItems()
         if not items:
             return
+        if not self._mqtt._client:
+            return
         for item in items:
             topic = item.text(0)
+            try:
                 if topic in self._custom_subs:
                     self._mqtt._client.unsubscribe(topic)
                     del self._custom_subs[topic]
                 idx = self._custom_sub_list.indexOfTopLevelItem(item)
                 self._custom_sub_list.takeTopLevelItem(idx)
                 self._log(f"[取消订阅] {topic}")
+            except Exception as e:
+                self._log(f"[取消订阅] 失败: {e}")
 
     # ================================================================
     # MQTT