Fix pretty printing of marc:leader (#550)

Author: dr0i

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

@@ -437,11 +437,11 @@ private void writeEscaped(final String str) {
         private void writeLeader() {
             final String leader = leaderBuilder.toString();
             if (leaderBuilder.length() > 0) {
-                prettyPrintIndentation();
+                prettyPrintIndentationLeader();
                 writeTagLeader(Tag.leader::open);
                 writeRawLeader(leader);
                 writeTagLeader(Tag.leader::close);
-                prettyPrintNewLine();
+                prettyPrintNewLineLeader();
             }
         }
 
@@ -462,12 +462,25 @@ private void prettyPrintIndentation() {
             }
         }
 
+        private void prettyPrintIndentationLeader() {
+            if (formatted) {
+                final String prefix = String.join("", Collections.nCopies(indentationLevel, INDENT));
+                writeRawLeader(prefix);
+            }
+        }
+
         private void prettyPrintNewLine() {
             if (formatted) {
                 builder.append(NEW_LINE);
             }
         }
 
+        private void prettyPrintNewLineLeader() {
+            if (formatted) {
+                writeRawLeader(NEW_LINE);
+            }
+        }
+
         private void sendAndClearData() {
             getReceiver().process(builder.toString());
             builder.delete(0, builder.length());