Fixed small oversight that would cause a filter to be overwritten wit…

…h null if it wasn't the last in the queue and would duplicate searchvalues

src/main/java/nl/nn/testtool/web/api/MetadataApi.java

@@ -70,13 +70,16 @@ public Response getMetadataList(@PathParam("storage") String storageName,
 
 		List<String> searchValues = new ArrayList<>();
 		for(String field : metadataNames) {
+			boolean changed = false;
 			for (int filterHeaderIndex = 0; filterHeaderIndex < filterHeaders.size(); filterHeaderIndex++) {
 				if (filterHeaders.get(filterHeaderIndex).equals(field)) {
 					searchValues.add(filterParams.get(filterHeaderIndex));
-				} else {
-					searchValues.add(null);
+					changed = true;
 				}
 			}
+			if(!changed) {
+				searchValues.add(null);
+			}
 		}
 		try {