form-item: fix #3226

packages/form/src/form-item.vue

@@ -164,7 +164,7 @@
         if (Array.isArray(value) && value.length > 0) {
           this.validateDisabled = true;
           prop.o[prop.k] = [];
-        } else if (value) {
+        } else if (value !== '') {
           this.validateDisabled = true;
           prop.o[prop.k] = this.initialValue;
         }