Throw error for optionality in distances

Change-Id: Ib555eef2cf512ce4bf443779096175c3009cc431
diff --git a/pom.xml b/pom.xml
index 4b2b844..31efb78 100644
--- a/pom.xml
+++ b/pom.xml
@@ -25,7 +25,7 @@
 
   <groupId>de.ids_mannheim.korap</groupId>
   <artifactId>Krill</artifactId>
-  <version>0.55.6</version>
+  <version>0.55.7</version>
   <packaging>jar</packaging>
 
   <name>Krill</name>