fix: gracefully handle portal element being removed from dom (#25)

src/portal-popper.spec.jsx

@@ -84,6 +84,7 @@ describe('<PortalPopper />', () => {
     expect(Popper.firstCall.args[2].modifiers.preventOverflow).to.eql({
       boundariesElement: 'boundary',
     })
+
     expect(Popper.firstCall.args[2].onCreate).to.be.a('function')
     expect(Popper.firstCall.args[2].onUpdate).to.be.a('function')
   })

src/portal.jsx

@@ -25,7 +25,11 @@ class Portal extends Component {
   componentWillUnmount () {
     const appendTo = this.props.appendTo
 
-    appendTo.removeChild(this._element)
+    // it's possible the element was removed from the dom or the dom has been
+    // blown away, which will cause `removeChild` to throw an exception
+    try {
+      appendTo.removeChild(this._element)
+    } catch (err) {} // eslint-disable-line no-empty
   }
 
   render () {

src/portal.spec.jsx

@@ -28,4 +28,14 @@ describe('<Portal />', () => {
     component.unmount()
     expect(document.getElementById('portal-0')).not.to.exist
   })
+
+  it('gracefully handles the portal div no longer existing on unmount', () => {
+    Portal.idNum = 0
+    const component = mount(<Portal />)
+
+    document.getElementById('portal-0').remove()
+
+    component.unmount() // should not error
+    expect(document.getElementById('portal-0')).not.to.exist
+  })
 })