Fixed incorrect initialization of nested-ref-collection-map

* The initialization of nestedRefCollectionMap[references-id]
  in handleReferences was the wrong place to initialize it since
  on pages with multiple <references /> tags, the map can get
  reset after a references tag is processed.  So, for later
  references tags, the entry for those will get cleared which
  led to crashes.

  Ex: es:Abderramán_I and couple others found in RT testing.

* This patch fixes the crasher.

* Added a new parser test with multiple references tags that
  captures this scenario. Regenerated selser changes file.

Change-Id: I64402e77996486b099acda114f2e250258b0048e