Remove redundant statement from Expansion algorithm

This addresses #165.

Author: lanthaler

spec/latest/json-ld-api/index.html

@@ -801,10 +801,6 @@ <h2>Expansion Algorithm</h2>
                otherwise set it to the result of expanding <em>property</em> according to the steps
                outlined in <a href="#iri-expansion">IRI Expansion</a> (passing <code>true</code> for
                the <em>vocabRelative</em> flag).</li>
-            <li>If <em>expanded property</em> is <tref>null</tref>, skip the
-              current <em>property</em>-<em>value</em> pair and continue to the
-              next <em>property</em>-<em>value</em> pair in <em>element</em>.
-            </li>
             <li>If <em>expanded property</em> is a <tref>keyword</tref>, process it as
               follows:
               <ol class="algorithm">
@@ -840,8 +836,9 @@ <h2>Expansion Algorithm</h2>
                 <li>Continue with the next <em>property</em>-<em>value</em> pair from <em>element</em>.</li>
               </ol>
             </li>
-            <li>If <em>expanded property</em> is not an <tref>absolute IRI</tref>,i.e., it doesn't contain a colon,
-              continue with the next member from <em>element</em>.</li>
+            <li>If <em>expanded property</em> is neither a <tref>blank node identifier</tref> nor an
+              <tref>absolute IRI</tref>,i.e., it is <tref>null</tref> or does not contain a colon
+              (<code>:</code>), continue with the next member from <em>element</em>.</li>
             <li>Otherwise, if <em>property's</em> <tref>container mapping</tref> is set to
               <code>@language</code>
               <ol class="algorithm">