Fixed major bug EXT-6786 ('Stand' button is corrupted if movement control floater is opened)

This issue is a regression of EXT-1655: Move Floater is notified about "not flying" after it was notified about "sitting".

Fix: taking into account siting mode while notifying about "flying".

Reviewed by Eugene Mutavchi at https://codereview.productengine.com/secondlife/r/233/

--HG--
branch : product-engine

indra/newview/llmoveview.cpp

@@ -200,7 +200,8 @@ void LLFloaterMove::setFlyingMode(BOOL fly)
 	if (instance)
 	{
 		instance->setFlyingModeImpl(fly);
-		instance->showModeButtons(!fly);
+		BOOL is_sitting = isAgentAvatarValid() && gAgentAvatarp->isSitting();
+		instance->showModeButtons(!fly && !is_sitting);
 	}
 	if (fly)
 	{