Revert the getChildMapping change since detecting nulls can't work.

Author: marnusw

src/ReactCSSTransitionReplace.jsx

@@ -20,16 +20,6 @@ import { nameShape } from './utils/PropTypes'
 const reactCSSTransitionReplaceChild = React.createFactory(ReactCSSTransitionReplaceChild)
 
 
-// Filter out nulls before looking for an only child
-function getChildMapping(children) {
-  if (!Array.isArray(children)) {
-    return children
-  }
-  const childArray = React.Children.toArray(children).filter(c => c)
-  return childArray.length === 1 ? childArray[0] : React.Children.only(childArray)
-}
-
-
 export default class ReactCSSTransitionReplace extends React.Component {
 
   static displayName = 'ReactCSSTransitionReplace'
@@ -64,7 +54,7 @@ export default class ReactCSSTransitionReplace extends React.Component {
 
     this.state = {
       currentKey: '1',
-      currentChild: getChildMapping(this.props.children),
+      currentChild: this.props.children ? React.Children.only(this.props.children) : undefined,
       prevChildren: {},
       height: null,
     }
@@ -87,7 +77,7 @@ export default class ReactCSSTransitionReplace extends React.Component {
   }
 
   componentWillReceiveProps(nextProps) {
-    const nextChild = getChildMapping(nextProps.children)
+    const nextChild = nextProps.children ? React.Children.only(nextProps.children) : undefined
     const {currentChild} = this.state
 
     if ((!currentChild && !nextChild) || (currentChild && nextChild && currentChild.key === nextChild.key)) {