[UI] null pointer exception (#6325)

dolphinscheduler-ui/src/js/conf/home/pages/security/pages/warningInstance/_source/createWarningInstance.vue

@@ -55,7 +55,7 @@
             </el-select>
           </template>
         </m-list-box-f>
-        <div  class="alertForm">
+        <div class="alertForm">
           <template>
             <form-create v-model="$f" :rule="rule" :option="{submitBtn:false}" size="mini"></form-create>
           </template>
@@ -127,6 +127,10 @@
             if (item.title.indexOf('$t') !== -1) {
               item.title = this.$t(item.field)
             }
+            // fix null pointer exception
+            if (!item.props) {
+              item.props = {}
+            }
           })
         }).catch(e => {
           this.$message.error(e.msg || '')