fix: prevent calling setState in TransitionGroup if it has been unmounted (#435)

Author: restlessbit

src/TransitionGroup.js

@@ -104,6 +104,11 @@ class TransitionGroup extends React.Component {
 
 componentDidMount(){
 this.appeared=true
+this.mounted=true
+}
+
+componentWillUnmount(){
+this.mounted=false
 }
 
 staticgetDerivedStateFromProps(
@@ -127,12 +132,14 @@ class TransitionGroup extends React.Component {
 child.props.onExited(node)
 }
 
-this.setState(state=>{
-letchildren={ ...state.children}
+if(this.mounted){
+this.setState(state=>{
+letchildren={ ...state.children}
 
-deletechildren[child.key]
-return{ children }
-})
+deletechildren[child.key]
+return{ children }
+})
+}
 }
 
 render(){