Fix#4112. Direct cause is that `applyStylesFromArray` tries to save and restore `activeSheetIndex`. However, if activeSheetIndex is -1, indicating no active sheet, the restore should not be attempted. Code is changed to test before attempting to restore.
The actual problem, however, is that user specified a sheet number for `addSheet`. That method will set activeSheetIndex most of the time, but this was a gap - when the supplied sheet number (0 in this case) is greater than activeSheetIndex (-1 in this case), it was leaving activeSheetIndex as -1. It is changed to set activeSheetIndex to 0 when activeSheetIndex is negative.
oleibman