fixed query expressions for collection selection (added quotes)

source/net/yacy/search/query/QueryModifier.java

@@ -202,13 +202,13 @@ public class QueryModifier {
         }
         StringBuilder filterQuery = new StringBuilder(20);
         if (sites.size() > 1) {
-            filterQuery.append('(').append(CollectionSchema.collection_sxt.getSolrFieldName()).append(':').append(sites.get(0));
+            filterQuery.append('(').append(CollectionSchema.collection_sxt.getSolrFieldName()).append(":\"").append(sites.get(0)).append('\"');
             for (int i = 1; i < sites.size(); i++) {
-                filterQuery.append(" OR ").append(CollectionSchema.collection_sxt.getSolrFieldName()).append(':').append(sites.get(i));
+                filterQuery.append(" OR ").append(CollectionSchema.collection_sxt.getSolrFieldName()).append(":\"").append(sites.get(i)).append('\"');
             }
             filterQuery.append(')');
         } else if (sites.size() == 1) {
-            filterQuery.append(CollectionSchema.collection_sxt.getSolrFieldName()).append(':').append(sites.get(0));
+            filterQuery.append(CollectionSchema.collection_sxt.getSolrFieldName()).append(":\"").append(sites.get(0)).append('\"');
         }
         return filterQuery.toString();