only flush if there is something to flush

.idea/runConfigurations/ElasticSearch_Tests__compress_.xml

@@ -34,7 +34,9 @@
     <RunnerSettings RunnerId="Profile ">
       <option name="myExternalizedOptions" value="&#10;additional-options2=onexit\=snapshot&#10;" />
     </RunnerSettings>
+    <RunnerSettings RunnerId="Run" />
     <ConfigurationWrapper RunnerId="Debug" />
+    <ConfigurationWrapper RunnerId="Run" />
     <method />
   </configuration>
 </component>

modules/elasticsearch/src/main/java/org/elasticsearch/common/compress/lzf/LZFOutputStream.java

@@ -82,7 +82,9 @@ public class LZFOutputStream extends OutputStream {
      * Compress and write the current block to the OutputStream
      */
     private void writeCompressedBlock() throws IOException {
+        if (position > 0) {
             encoder.encodeChunk(outputStream, outputBuffer, 0, position);
             position = 0;
         }
     }
+}

modules/elasticsearch/src/main/java/org/elasticsearch/common/io/stream/LZFStreamOutput.java

@@ -103,7 +103,9 @@ public class LZFStreamOutput extends StreamOutput {
      * Compress and write the current block to the OutputStream
      */
     private void writeCompressedBlock() throws IOException {
+        if (position > 0) {
             encoder.encodeChunk(out, outputBuffer, 0, position);
             position = 0;
         }
     }
+}