feat(timeseries): Do not hide (only disable) dropdown for pest before culture is selected

src/components/ObservationTimeSeries.vue

@@ -47,10 +47,10 @@
       <label for="cropId">{{ this.$i18n.t("observationTimeSeries.selectcrop") }}</label>
     </div>
 
-    <div class="form-floating mb-3" v-if="dataToSubmit.cropId > 0">
+    <div class="form-floating mb-3">
       <select id="pestId" class="form-select" required
               v-model="dataToSubmit.pestId"
-              :disabled="uneditable()">
+              :disabled="dataToSubmit.cropId < 0 || uneditable()">
         <option v-for="pest in formOptions.pests" v-bind:value="pest.pestId">{{ pest.pestName }}</option>
       </select>
       <label for="pestId">{{ this.$i18n.t("observationTimeSeries.selectpest") }}</label>