Fixed major bug EXT-6092 [crashhunters] Crash in LLFlatListView::selectItemPair

Reason:
 A) incorrect UP arrow handling in accordion control: invisible accordion tab was selected to handle selection.
 B) invalid std::map item (in empty map) was used to make selection in Flat List

Fix: added checks against empty map before use front/back item pair before selecting first/last items.
Also updated processing of the UP key in accordion control to not select invisible accordion tab.

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/318/

--HG--
branch : product-engine

indra/llui/llaccordionctrl.cpp

@@ -668,15 +668,23 @@ S32	LLAccordionCtrl::notifyParent(const LLSD& info)
 				LLAccordionCtrlTab* accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
 				if(accordion_tab->hasFocus() && i>0)
 				{
+					bool prev_visible_tab_found = false;
 					while(i>0)
 					{
 						if(mAccordionTabs[--i]->getVisible())
+						{
+							prev_visible_tab_found = true;
 							break;
+						}
 					}
-					
-					accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
-					accordion_tab->notify(LLSD().with("action","select_last"));
-					return 1;
+
+					if (prev_visible_tab_found)
+					{
+						accordion_tab = dynamic_cast<LLAccordionCtrlTab*>(mAccordionTabs[i]);
+						accordion_tab->notify(LLSD().with("action","select_last"));
+						return 1;
+					}
+					break;
 				}
 			}
 			return 0;

indra/llui/llflatlistview.cpp

@@ -744,12 +744,18 @@ LLRect LLFlatListView::getLastSelectedItemRect()
 
 void LLFlatListView::selectFirstItem	()
 {
+	// No items - no actions!
+	if (mItemPairs.empty()) return;
+
 	selectItemPair(mItemPairs.front(), true);
 	ensureSelectedVisible();
 }
 
 void LLFlatListView::selectLastItem		()
 {
+	// No items - no actions!
+	if (mItemPairs.empty()) return;
+
 	selectItemPair(mItemPairs.back(), true);
 	ensureSelectedVisible();
 }