Bug 13994: Add a back link to error message in Reports

To reproduce:
- Go to Home > Reports
- Create from SQL
- Do something that results in an error message, e.g. by entering an UPDATE statement

Result: You get an error message with title "The follwing error was encountered"
But there is now link to go directly back to fix it.

To test:
- Apply patch
- Repeat steps above
- Verify that a link appears (and works): "Back to previous page"

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>

koha-tmpl/intranet-tmpl/prog/en/modules/reports/guided_reports_start.tt

@@ -1004,6 +1004,9 @@ Sub report:<select name="subreport">
     [% ELSIF ( error.cache_expiry ) %]Please select a cache expiry less than 30 days.
     [% ELSE %]
     [% END %]
+    <div id="onerror_actions">
+        <a href="javascript:window.history.back()" class="button">Back to previous page</a>
+    </div>
 [% END %]
 </div>
 <fieldset class="action"><input type="hidden" name="phase" value="Use saved" />