handle falsey values correctly in coerce2

Author: alexcjohnson

src/lib/coerce.js

@@ -315,9 +315,10 @@ exports.coerce = function(containerIn, containerOut, attributes, attribute, dflt
  */
 exports.coerce2 = function(containerIn, containerOut, attributes, attribute, dflt) {
     var propIn = nestedProperty(containerIn, attribute),
-        propOut = exports.coerce(containerIn, containerOut, attributes, attribute, dflt);
+        propOut = exports.coerce(containerIn, containerOut, attributes, attribute, dflt),
+        valIn = propIn.get();
 
-    return propIn.get() ? propOut : false;
+    return (valIn !== undefined && valIn !== null) ? propOut : false;
 };
 
 /*

test/jasmine/tests/lib_test.js

@@ -674,7 +674,7 @@ describe('Test lib.js:', function() {
 
             it('should set a value and return the value it sets when user input is valid', function() {
                 var colVal = 'red',
-                    sizeVal = 14,
+                    sizeVal = 0, // 0 is valid but falsey
                     attrs = {testMarker: {testColor: {valType: 'color', dflt: 'rgba(0, 0, 0, 0)'},
                         testSize: {valType: 'number', dflt: 20}}},
                     obj = {testMarker: {testColor: colVal, testSize: sizeVal}},
@@ -706,7 +706,7 @@ describe('Test lib.js:', function() {
 
             it('should return false if there is no user input', function() {
                 var colVal = null,
-                    sizeVal = null,
+                    sizeVal, // undefined
                     attrs = {testMarker: {testColor: {valType: 'color', dflt: 'rgba(0, 0, 0, 0)'},
                         testSize: {valType: 'number', dflt: 20}}},
                     obj = {testMarker: {testColor: colVal, testSize: sizeVal}},