Link generation and pop-up windows

[Jack Ireland]

 - link button did not work after popping up a sunspot pop-up window.
 example: go back one year, click on the sunspot marker to pop up a window, close the window, and then
 click the link button
 also, if the link button is pressed before the sunpot pop-up window is launched, then the link button
 works as expected even after a pop-up window is launched.

[Jeff Stys (jstys-z)]

This is a pre-existing bug, unrelated to the F/E implementation in development. The behavior described below can be reproduced with the production code on Helioviewer.org:

The failure of the link button can be traced to an undefined date being passed into Date.parseUTCDate().
This occurs when the array of image tile layers in the TileLayerManager is empty (all tile layer accordions have been removed from the UI).

The getMiddleObservationTime() method currently only handles cases where there are 1 or more image tile layers selected. It attempts to access the date corresponding to the first element in an empty array and then passes that undefined value to Date.parseUTCDate() which throws an exception.

[Jeff Stys (jstys-z)]

+ Updated HeliovewerWebClient.js::getMiddleObservationTime() in the HEK development code to use the value of requestDate when no image tile layers are enabled.