Don't allow colliding flat meta values

Change-Id: Id280934f813a67eff3dd2a1ba84a1b876906910d
diff --git a/src/main/java/de/ids_mannheim/korap/response/Text.java b/src/main/java/de/ids_mannheim/korap/response/Text.java
index 68dab3c..dc77603 100644
--- a/src/main/java/de/ids_mannheim/korap/response/Text.java
+++ b/src/main/java/de/ids_mannheim/korap/response/Text.java
@@ -55,11 +55,11 @@
             // Legacy flat field support
             String mfs = mf.key;
             String value = this.getFieldValue(mfs);
-            if (value != null)
+            if (value != null && !json.has(mfs))
                 json.set(mfs, new TextNode(value));
 		};
 
-        this.addMessage(0, "Support for flat field values is eprecated");
+        this.addMessage(0, "Support for flat field values is deprecated");
 
         
         // Match was no match