Fix assert after failed login.

reset_login(), among others, sets the state back to STATE_LOGIN_SHOW,
which then causes gViewerWindow->initWorldUI() to be called, which
is the (only) function that calls
LLMenuOptionPathfindingRebakeNavmesh::initialize.
In other words, it's perfectly normal to enter that function
a second time and the assert is erroneous.

indra/newview/llmenuoptionpathfindingrebakenavmesh.cpp

@@ -70,7 +70,6 @@ LLMenuOptionPathfindingRebakeNavmesh::~LLMenuOptionPathfindingRebakeNavmesh()
 
 void LLMenuOptionPathfindingRebakeNavmesh::initialize()
 {
-	llassert(!mIsInitialized);
 	if (!mIsInitialized)
 	{
 		mIsInitialized = true;