Fix SkipMultiCursor behavior when there is no selection

When there is no selection (i.e. selection is empty), SkipMultiCursor
searches for the empty text, "finds" it as the beginning of the buffer,
and as a result, jumps to the beginning of the buffer, which confuses
the user. Fix it.

internal/action/actions.go

@@ -2013,6 +2013,9 @@ func (h *BufPane) MouseMultiCursor(e *tcell.EventMouse) bool {
 // SkipMultiCursor moves the current multiple cursor to the next available position
 func (h *BufPane) SkipMultiCursor() bool {
 	lastC := h.Buf.GetCursor(h.Buf.NumCursors() - 1)
+	if !lastC.HasSelection() {
+		return false
+	}
 	sel := lastC.GetSelection()
 	searchStart := lastC.CurSelection[1]