Don't write footer when record is empty (#543)

Author: dr0i

metafacture-biblio/src/main/java/org/metafacture/biblio/marc21/MarcXmlEncoder.java

@@ -372,7 +372,9 @@ protected void onResetStream() {
 
         @Override
         protected void onCloseStream() {
-            writeFooter();
+            if (!atStreamStart) {
+                writeFooter();
+            }
             sendAndClearData();
         }
 

metafacture-biblio/src/test/java/org/metafacture/biblio/marc21/MarcXmlEncoderTest.java

@@ -389,4 +389,11 @@ public void shouldNotEncodeNestedTypeLiteralAsAttribute() {
         assertEquals(expected, actual);
     }
 
+    @Test
+    public void issue543_shouldNotWriteFooterWhenRecordIsEmpty() {
+        encoder.closeStream();
+        String actual = resultCollector.toString();
+        assertTrue(actual.isEmpty());
+    }
+
 }