Improve charset encoder

Change-Id: I833b5cee3044dc47712f528327908096f714966a
diff --git a/src/main/java/de/ids_mannheim/korap/plkexport/RtfExporter.java b/src/main/java/de/ids_mannheim/korap/plkexport/RtfExporter.java
index 8422ca7..edc20cc 100644
--- a/src/main/java/de/ids_mannheim/korap/plkexport/RtfExporter.java
+++ b/src/main/java/de/ids_mannheim/korap/plkexport/RtfExporter.java
@@ -275,6 +275,8 @@
         if (rawText == null)
             return;
 
+        charsetEncoder.reset();
+
         char c;
         for (int i = 0; i < rawText.length(); i++) {
             c = rawText.charAt( i );