fix def value

Author: jogibear9988

src/PropertyGrid.ts

@@ -266,12 +266,12 @@ export class PropertyGrid extends BaseCustomWebComponentConstructorAppend {
                         const pInfo = <IProperty>node.data.property;
                         const ctl = await this.getEditorForType(pInfo, currentValue, pPath, e);
                         if (ctl) {
-                            if (pInfo.defaultValue && ctl instanceof HTMLInputElement && ctl.value == '' && !pInfo.nullable) {
+                            if (pInfo.defaultValue != null && ctl instanceof HTMLInputElement && ctl.value == '' && !pInfo.nullable) {
                                 if (ctl.type == 'text')
                                     ctl.placeholder = pInfo.defaultValue;
                                 else
                                     ctl.value = pInfo.defaultValue;
-                            } else if (pInfo.defaultValue && ctl instanceof HTMLSelectElement && ctl.value == '' && !pInfo.nullable) {
+                            } else if (pInfo.defaultValue != null && ctl instanceof HTMLSelectElement && ctl.value == '' && !pInfo.nullable) {
                                 ctl.value = pInfo.defaultValue;
                             }
                             ctl.style.flexGrow = '1';