Fix width being ignored when has a value of 0

8f6a96adbc added a test in isDimDefined that checks if `value > 0.0`, but unfortunately, it did not faithfully port the JavaScript version which is `value >= 0.0`. Sadly, no test covered this so it went unnoticed.

dist/css-layout.h

@@ -613,7 +613,7 @@ static float getDimWithMargin(css_node_t *node, css_flex_direction_t axis) {
 
 static bool isDimDefined(css_node_t *node, css_flex_direction_t axis) {
   float value = node->style.dimensions[dim[axis]];
-  return !isUndefined(value) && value > 0.0;
+  return !isUndefined(value) && value >= 0.0;
 }
 
 static bool isPosDefined(css_node_t *node, css_position_t position) {

dist/css-layout.js

@@ -1095,7 +1095,7 @@ var computeLayout = (function() {
 })();
 
 // This module export is only used for the purposes of unit testing this file. When
-// the library is packaged this file is included within css-layout.js which forms 
+// the library is packaged this file is included within css-layout.js which forms
 // the public API.
 if (typeof exports === 'object') {
   module.exports = computeLayout;