while trying to fetch transitions on the newest piwik version (2.8.3) i get

There's no data for http:​/​/base url/​Gene Full Report Records

Either the action had no pageviews during the period
or it is invalid.
Go back to the previous action

when i click on a transition report in either the pages, or entry pages widget.

looking into it a bit more, the request:

http://piwik_url/index.php?date=2014-10-26&actionType=url&actionName=http%3A%2F%2Fbase_url%2FGene+Full+Report+Records&expanded=1&format=JSON&module=API&method=Transitions.getTransitionsForAction&idSite=1&period=day

results in
{"result":"error","message":"NoDataForAction"}

/////

it seems that there is an escaping issue here. if i naively escape my url (just needs spaces) here:

plugins/Transitions/API.php

137                 if ($id < 0) {
138                     $escapedPath = str_replace(" ","%20",$actionName);
139                     $id = TableLogAction::getIdActionFromSegment($escapedPath, 'idaction_url', SegmentExpression::MATCH_EQUAL, 'pageUrl');
140                 }  

then deriveIdAction succeeds (although the fetch still fails in addInternalReferrers farther down the road, i haven't continued to look into it.)

here is what the url looks like in mysql:

mysql> SELECT idaction, type, name FROM piwik_log_action limit 100
-> ;
+----------+------+-----------------------------------------------------------------------------------+
| idaction | type | name |
+----------+------+-----------------------------------------------------------------------------------+
...
| 3 | 1 | base_url/Gene%20Full%20Report%20Records