fixed exception during finalize when statement AND db is already closed (#342)

Author: b3nn0

src/main/java/org/sqlite/core/CoreStatement.java

@@ -116,11 +116,10 @@ protected boolean exec(String sql) throws SQLException {
     }
 
     protected void internalClose() throws SQLException {
-        if (conn.isClosed())
-            throw DB.newSQLException(SQLITE_ERROR, "Connection is closed");
-
         if (pointer == 0)
             return;
+        if (conn.isClosed())
+            throw DB.newSQLException(SQLITE_ERROR, "Connection is closed");
 
         rs.close();