Return an empty array instead of null

`forEach` won't iterate over an empty array so this is better than
returning a falsey value and checking for it.

Author: simonsmith

lib/validate-selectors.js

@@ -41,7 +41,7 @@ function getSelectors(rule) {
   // Skip validation on rules with no declarations
   // as these don't exist after rules have been unwrapped
   if (hasNoDeclarations(rule)) {
-    return null;
+    return [];
   }
 
   if (isNestedRule(rule)) {
@@ -75,8 +75,6 @@ module.exports = function(config) {
     : toInterpoloatedRegexp(initialPattern);
   var selectors = getSelectors(rule);
 
-  if (!selectors) {return;}
-
   selectors.forEach(function(selector) {
     // Don't bother with :root
     if (selector === ':root') return;

test/nesting.js

@@ -22,7 +22,7 @@ describe('getSelectors function', function() {
       componentRoot.append({selector: '.Component-d'});
       componentRoot.append({text: 'comment'});
 
-      assert.deepEqual(getSelectors(componentRoot), null);
+      assert.deepEqual(getSelectors(componentRoot), []);
     });
 
     it('should return a selector if the ruleset has declarations', function() {
@@ -56,8 +56,8 @@ describe('getSelectors function', function() {
       descendant.append([hover, state]);
       componentRoot.append(descendant);
 
-      assert.deepEqual(getSelectors(componentRoot), null);
-      assert.deepEqual(getSelectors(descendant), null);
+      assert.deepEqual(getSelectors(componentRoot), []);
+      assert.deepEqual(getSelectors(descendant), []);
       assert.deepEqual(getSelectors(hover), ['.Component .Component-d:hover']);
       assert.deepEqual(getSelectors(state), ['.Component .Component-d.is-active']);
     });
@@ -70,7 +70,7 @@ describe('getSelectors function', function() {
         componentRoot.append([hover, state]);
         root.append(componentRoot);
 
-        assert.deepEqual(getSelectors(componentRoot), null);
+        assert.deepEqual(getSelectors(componentRoot), []);
         assert.deepEqual(getSelectors(hover), ['.Component:hover', '.Component-d:hover']);
         assert.deepEqual(getSelectors(state), ['.Component.is-active', '.Component-d.is-active']);
       });
@@ -97,7 +97,7 @@ describe('getSelectors function', function() {
       componentRoot.append(rule);
       media.append(componentRoot);
 
-      assert.deepEqual(getSelectors(componentRoot), null);
+      assert.deepEqual(getSelectors(componentRoot), []);
       assert.deepEqual(getSelectors(rule), ['.Component .Component-d']);
     });
   });
@@ -110,7 +110,7 @@ describe('getSelectors function', function() {
       componentRoot.append(media);
 
       assert.deepEqual(getSelectors(rule), ['.Component .Component-d']);
-      assert.deepEqual(getSelectors(componentRoot), null);
+      assert.deepEqual(getSelectors(componentRoot), []);
     });
 
     it('should return a selector for a ruleset with declarations and nested media query', function() {