Fix use-after-free which may happen during shutdown

If a module, e.g. keepnick, tries to remove a timer in
OnIRCDisconnected.

Thanks to KindOne for the report.

modules/keepnick.cpp

@@ -121,7 +121,7 @@ class CKeepNickMod : public CModule {
 			return;
 
 		m_pTimer->Stop();
-		RemTimer(m_pTimer->GetName());
+		RemTimer(m_pTimer);
 		m_pTimer = NULL;
 	}
 

src/znc.cpp

@@ -51,6 +51,11 @@ CZNC::~CZNC() {
 
 	for (map<CString,CUser*>::iterator a = m_msUsers.begin(); a != m_msUsers.end(); ++a) {
 		a->second->GetModules().UnloadAll();
+
+		const vector<CIRCNetwork*>& networks = a->second->GetNetworks();
+		for (vector<CIRCNetwork*>::const_iterator b = networks.begin(); b != networks.end(); ++b) {
+			(*b)->GetModules().UnloadAll();
+		}
 	}
 
 	for (size_t b = 0; b < m_vpListeners.size(); b++) {