xrGame: fix ability to get a negative money balance after paid service

Why:
Money was checked when player press to a some question in dialog. If player by buy something at this moment, then your money state will be changed, but a condition for a service dialog wil not be rechecked.

How:
Just reset a talk dialog state to initial when player press to a trade button.

Issue: OpenXRay#1173

src/xrGame/ui/UITalkWnd.cpp

@@ -323,6 +323,7 @@ void CUITalkWnd::SwitchToTrade()
         {
             UITalkDialogWnd->Hide();
             StopSnd();
+            InitTalkDialog();
 
             pGameSP->StartTrade(m_pOurInvOwner, m_pOthersInvOwner);
         }