remove empty media queries

__tests__/sanity.test.js

@@ -17,3 +17,11 @@ it('generates the right CSS', () => {
       expect(result.css).toBe(expected)
     })
 })
+
+it('Does not add something if not used at all', () => {
+  return postcss([tailwind()])
+    .process('')
+    .then(result => {
+      expect(result.css).toBe('')
+    })
+})

src/lib/substituteResponsiveAtRules.js

@@ -29,7 +29,11 @@ export default function(config) {
           return cloned
         })
       )
-      css.append(mediaQuery)
+
+      if(mediaQuery.nodes.length) {
+        // do not add media query without any rules or comments
+        css.append(mediaQuery)
+      }
     })
   }
 }