下面是我的带有vuejs的前端模板

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<template>
  <div class="d-flex justify-content-center">
    <form
      @submit.prevent="submit"
      enctype="multipart/form-data"
      class="largeur80 my-5 shadow bordurePost bordureRond"
    >
      <div class="form-group">
        <label class="text-primary" for="titre">Titre du post</label>
        <input
          type="text"
          class="form-control"
          name="titre"
          placeholder="title..."
          v-model.trim="$v.titre.$model"
        />
      </div>
      <div class="error" v-if="!$v.titre.required && submitStatus === 'ERROR'">
        Field is required
      </div>
      <div class="form-group">
        <label class="text-primary" for="description">Description</label>
        <textarea
          class="form-control"
          name="description"
          rows="3"
          placeholder="Décrire le post..."
          v-model.trim="$v.description.$model"
        ></textarea>
      </div>
      <div
        class="error"
        v-if="!$v.description.required && submitStatus === 'ERROR'"
      >
        Field is required
      </div>
      <div class="form-group">
        <label class="text-primary" for="image_link"
          >Ajouter une image ou multimedia</label
        >
        <input type="file" ref="image" class="file-input" @change="upload" />
      </div>
      <!--
      <div
        class="error"
        v-if="!$v.image_link.required && submitStatus === 'ERROR'"
      >
        Field is required
      </div>
      -->
      <div
        class="form-group row d-flex align-item-center justify-content-center"
      >
        <div class="col-sm-10 ">
          <button
            type="submit"
            class="bg-light btn btn-outline-primary"
            :disabled="submitStatus === 'PENDING'"
          >
            Publier !
          </button>
          <p class="typo__p" v-if="submitStatus === 'OK'">
            Thanks for your submission!
          </p>
          <p class="typo__p" v-if="submitStatus === 'ERROR'">
            Please fill the form correctly.
          </p>
          <p class="typo__p" v-if="submitStatus === 'ERROR SERVEUR'">
            erreur serveur:Le mot de passe ou l'email ne correponde pas OU
            server HS !
          </p>
          <p class="typo__p" v-if="submitStatus === 'PENDING'">Sending...</p>
        </div>
      </div>
    </form>
  </div>
</template>

<script>
import { required, maxLength } from "vuelidate/lib/validators";
import axios from "axios";
export default {
  name: "envoyer",

  data() {
    return {
      image: null,
      titre: "",
      description: "",
      image_link: null || "",
      user_id: localStorage.getItem("userId") || null,
      submitStatus: null,
    };
  },
  validations: {
    titre: { required, maxLength: maxLength(100) },
    description: { required, maxLength: maxLength(500) },
    image_link: {},
  },

  methods: {
    upload() {
      this.image = this.$refs.image.files[0];
      console.log(this.image);
    },

    submit() {
      const formData = new FormData();
      if (this.image !== null || "") {
        formData.append("image", this.image, this.image.filename);
        formData.append("titre", this.titre);
        formData.append("description", this.description);
        formData.append("user_id", this.user_id);
      } else {
        formData.append("titre", this.titre);
        formData.append("description", this.description);
        formData.append("user_id", this.user_id);
      }

      console.log("requete ver serveur!");
      this.$v.$touch();
      if (this.$v.$invalid) {
        this.submitStatus = "ERROR";
        console.log("A echouer informations non complete!");
      } else {
        // do your submit logic here
        console.log("En attente");
        this.submitStatus = "PENDING";

        axios
          .post(
            "http://localhost:3000/poste",
            formData
            //titre: this.titre,
            // description: this.description,
            // user_id: this.user_id,
          )
          .then((response) => {
            (this.submitStatus = "OK"), console.log(response);
            console.log(formData);
            //this.$router.go("/post");
          })

          .catch(
            (error) => (
              (this.submitStatus = "ERROR SERVEUR"), console.log(error)
            )
          );
      }
    },
  },
};
</script>

<style></style>

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这是我的后端，当它没有收到一个映像，服务器崩溃，因为文件名不存在，所以我应该做什么，以便没有问题，当用户没有发送文件

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const mysql = require("mysql");
const Poste = require("../models/post");

// Create and Save a new Poste
exports.create = (req, res) => {
  // Validate request
  if (!req.body) {
    res.status(400).send({
      message: "Content can not be empty!",
    });
  }

  // Create a Poste
  const poste = new Poste({
    titre: req.body.titre,
    description: req.body.description,
    image_link: `${req.protocol}://${req.get("host")}/images/${
      req.file.filename
    }`,
    nb_commentaires: req.body.nb_commentaires,
    nb_likes: req.body.nb_likes,
    nb_dislikes: req.body.nb_dislikes,
    user_id: req.body.user_id,
    date_cree: new Date(),
  });

  // Save Poste in the database
  Poste.create(poste, (err, data) => {
    if (err)
      res.status(500).send({
        message: err.message || "Some error occurred while creating the Poste.",
      });
    else res.send(data);
  });
};

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当我发送所有内容时，它工作得很好，但当我只发送标题和描述时，服务器就会崩溃，我该怎么办？？？？