Sample scenario: 6 MP Age of Discovery.biq (custom rules and players)
Expected: Works! Actual: Unexpected error: java.lang.ArrayIndexOutOfBoundsException: -1 at java.util.ArrayList.elementData(ArrayList.java:422) at java.util.ArrayList.get(ArrayList.java:435) at com.civfanatics.civ3.xplatformeditor.PLYRTab.refreshSelectedIndices(PLYRTab.java:1238)
Confirmed on Windows 8/JDK 8 and OS X/Java 9.
Turns out that there is no functional impact, as this error (and another case when deleting the tech) occurs at the very end of the tech-to-do-list, and the player tab always refreshes the starting tech list when switched to anyway. Cleaned it up anyway, since it looks alarming and isn't great behavior; also cleaned up a bunch of sysouts relating to drag-and-drop while I was at it.
Fixed in 1.29.