Fix error when clearing by null value (#391)

Author: jordanmkoncz

src/index.js

@@ -554,7 +554,7 @@ class PhoneInput extends React.Component {
  // we don't need to send the whole number to guess the country... only the first 6 characters are enough
  // the guess country function can then use memoization much more effectively since the set of input it
  // gets has drastically reduced
- if (!this.state.freezeSelection || selectedCountry.dialCode.length > inputNumber.length) {
+ if (!this.state.freezeSelection || (!!selectedCountry && selectedCountry.dialCode.length > inputNumber.length)) {
  if (this.props.disableCountryGuess) {newSelectedCountry = selectedCountry;}
  else {
  newSelectedCountry = this.guessSelectedCountry(inputNumber.substring(0, 6), country, onlyCountries, hiddenAreaCodes) || selectedCountry;