simple fix for colon use in SQL select statement

jdbc-query/src/main/java/org/xbib/jdbc/query/MixedParameterSql.java

@@ -65,19 +65,21 @@ public class MixedParameterSql {
                 }
                 newSql.append(sql, searchIndex, nextColonIndex);
                 String paramName = sql.substring(nextColonIndex + 1, endOfNameIndex);
-                boolean secretParam = paramName.startsWith("secret");
-                Object arg = nameToArg.get(paramName);
-                if (arg instanceof RewriteArg) {
-                    newSql.append(((RewriteArg) arg).getSql());
-                    rewrittenArgs.add(paramName);
-                } else {
-                    newSql.append('?');
-                    if (nameToArg.containsKey(paramName)) {
-                        argsList.add(secretParam ? new SecretArg(arg) : arg);
+                if (!"".equals(paramName)) {
+                    boolean secretParam = paramName.startsWith("secret");
+                    Object arg = nameToArg.get(paramName);
+                    if (arg instanceof RewriteArg) {
+                        newSql.append(((RewriteArg) arg).getSql());
+                        rewrittenArgs.add(paramName);
                     } else {
-                        throw new DatabaseException("The SQL requires parameter ':" + paramName + "' but no value was provided");
+                        newSql.append('?');
+                        if (nameToArg.containsKey(paramName)) {
+                            argsList.add(secretParam ? new SecretArg(arg) : arg);
+                        } else {
+                            throw new DatabaseException("The SQL requires parameter ':" + paramName + "' but no value was provided");
+                        }
+                        argNamesList.add(paramName);
                     }
-                    argNamesList.add(paramName);
                 }
                 searchIndex = endOfNameIndex;
             } else {