Malformed pagination link on context search results

When context search returns results paginated the navigation links are broken:
e.g.:  http://diccionariobenasques.com/index.jsp?mode=context&word=casa

current link to page 2
```
http://diccionariobenasques.com/index.jsp?word=casa&cnt=Contextual&pag=2
```
correct link to page 2
```
http://diccionariobenasques.com/index.jsp?word=casa&mode=context&pag=2
```