Fixed block map prepare value (where the colon goes)

src/emitter.cpp

@@ -372,6 +372,9 @@ namespace YAML
         const unsigned nextIndent = curIndent + m_pState->CurGroupIndent();
         const std::size_t childCount = m_pState->CurGroupChildCount();
         
+        if(child == EmitterNodeType::None)
+            return;
+
         if(!m_pState->HasBegunNode()) {
             if(childCount > 0) {
                 m_stream << "\n";
@@ -400,10 +403,12 @@ namespace YAML
         const unsigned curIndent = m_pState->CurIndent();
         const unsigned nextIndent = curIndent + m_pState->CurGroupIndent();
 
+        if(!m_pState->HasBegunNode()) {
             if(false /* was long key */) {
             } else {
                 m_stream << ":";
             }
+        }
         
         switch(child) {
             case EmitterNodeType::None: