Fix for value prop being set to zero

The test for a single value of 0 was already there, and it caught the bug for the simple 
test of `if (!value) ...`.  Yay for tests :)

src/Select.js

@@ -297,7 +297,7 @@ const Select = React.createClass({
 		if (this.props.multi) {
 			if (typeof value === 'string') value = value.split(this.props.delimiter);
 			if (!Array.isArray(value)) {
-				if (!value) return [];
+				if (value === null || value === undefined) return [];
 				value = [value];
 			}
 			return value.map(this.expandValue).filter(i => i);

test/Select-test.js

@@ -469,7 +469,19 @@ describe('Select', () => {
 					]);
 			});
 
-			it('supports updating the value to 0', () => {
+			it('supports updating the value to a single value', () => {
+
+				wrapper.setPropsForChild({
+					value: 1
+				});
+
+				expect(ReactDOM.findDOMNode(instance), 'queried for', '.Select-value .Select-value-label',
+					'to satisfy', [
+						expect.it('to have text', 'One')
+					]);
+			});
+
+			it('supports updating the value to single value of 0', () => {
 
 				// This test is specifically in case there's a "if (value) {... " somewhere
 				wrapper.setPropsForChild({