Fix: Guard against 'null' description when losing focus (fixes #19) (#20

)

There is an issue where if you search and render suggestions for the
first time (i.e. a suggestion hasn't been selected yet) and click away
so taht focus is lost then you will receive an error of the form:
"Uncaught TypeError: Cannot read property 'description' of null". This
error occurs in the function we pass to the 'itemToString' prop when
rendering the <Downshift> component. Its a result of no suggestions
being available yet trying to destructure the 'description' property off
of a suggestion.

This commit provides a fix to guard against the case where there are no
suggestions, in which case we simply return the empty string.
	modified:   src/MUIPlacesAutocomplete.jsx

src/MUIPlacesAutocomplete.jsx

@@ -258,7 +258,7 @@ export default class MUIPlacesAutocomplete extends React.Component {
       <Downshift
         onSelect={this.onSuggestionSelected}
         onInputValueChange={this.onInputValueChange}
-        itemToString={({ description }) => description}
+        itemToString={suggestion => (suggestion ? suggestion.description : '')}
         render={this.renderAutocomplete}
       />
     )