Fix trailing space when parent selector is the last part of the selector.

'''
.foo {
  .bar & {
    &:hover {
      color: orange;
    }
  }
}
'''

now outputs

'''
.bar .foo:hover {
  color: orange;
}
'''

Author: jamesfoster

lib/less/tree/element.js

@@ -19,7 +19,12 @@ tree.Element.prototype.eval = function (env) {
                              this.index);
 };
 tree.Element.prototype.toCSS = function (env) {
-    return this.combinator.toCSS(env || {}) + (this.value.toCSS ? this.value.toCSS(env) : this.value);
+	var value = (this.value.toCSS ? this.value.toCSS(env) : this.value);
+	if (value == '' && this.combinator.value.charAt(0) == '&') {
+		return '';
+	} else {
+		return this.combinator.toCSS(env || {}) + value;
+	}
 };
 
 tree.Combinator = function (value) {