- Used classnames to handle undefined classname (Hacker0x01#1896)

Author: enagy27

src/index.jsx

@@ -733,7 +733,7 @@ export default class DatePicker extends React.Component {
       placeholder: this.props.placeholderText,
       disabled: this.props.disabled,
       autoComplete: this.props.autoComplete,
-      className: customInput.props.className + " " + className,
+      className: classnames(customInput.props.className, className),
       title: this.props.title,
       readOnly: this.props.readOnly,
       required: this.props.required,