diff --git a/src/Entities.cpp b/src/Entities.cpp
index bd97981..63a4a64 100644
--- a/src/Entities.cpp
+++ b/src/Entities.cpp
@@ -16,8 +16,9 @@ EntityRef::EntityRef(CNSocket *s) {
 EntityRef::EntityRef(int32_t i) {
     id = i;
 
-    assert(NPCManager::NPCs.find(id) != NPCManager::NPCs.end());
-    kind = NPCManager::NPCs[id]->kind;
+    kind = EntityKind::INVALID;
+    if (NPCManager::NPCs.find(id) != NPCManager::NPCs.end())
+        kind = NPCManager::NPCs[id]->kind;
 }
 
 bool EntityRef::isValid() const {
diff --git a/src/Groups.cpp b/src/Groups.cpp
index ac58d6e..8d948b8 100644
--- a/src/Groups.cpp
+++ b/src/Groups.cpp
@@ -64,6 +64,9 @@ static void attachGroupData(std::vector<EntityRef>& pcs, std::vector<EntityRef>&
 }
 
 void Groups::addToGroup(Group* group, EntityRef member) {
+    if (group == nullptr)
+        return;
+
     if (member.kind == EntityKind::PLAYER) {
         Player* plr = PlayerManager::getPlayer(member.sock);
         plr->group = group;
@@ -109,6 +112,9 @@ void Groups::addToGroup(Group* group, EntityRef member) {
 }
 
 bool Groups::removeFromGroup(Group* group, EntityRef member) {
+    if (group == nullptr)
+        return false;
+
     if (member.kind == EntityKind::PLAYER) {
         Player* plr = PlayerManager::getPlayer(member.sock);
         plr->group = nullptr; // no dangling pointers here muahaahahah
@@ -168,6 +174,9 @@ bool Groups::removeFromGroup(Group* group, EntityRef member) {
 }
 
 void Groups::disbandGroup(Group* group) {
+    if (group == nullptr)
+        return;
+
     // remove everyone from the group!!
     bool done = false;
     while(!done) {
@@ -252,6 +261,9 @@ static void leaveGroup(CNSocket* sock, CNPacketData* data) {
 }
 
 void Groups::sendToGroup(Group* group, void* buf, uint32_t type, size_t size) {
+    if (group == nullptr)
+        return;
+
     auto players = group->filter(EntityKind::PLAYER);
     for (EntityRef ref : players) {
         ref.sock->sendPacket(buf, type, size);
@@ -259,6 +271,9 @@ void Groups::sendToGroup(Group* group, void* buf, uint32_t type, size_t size) {
 }
 
 void Groups::sendToGroup(Group* group, EntityRef excluded, void* buf, uint32_t type, size_t size) {
+    if (group == nullptr)
+        return;
+
     auto players = group->filter(EntityKind::PLAYER);
     for (EntityRef ref : players) {
         if(ref != excluded) ref.sock->sendPacket(buf, type, size);
@@ -294,6 +309,9 @@ void Groups::groupTickInfo(CNSocket* sock) {
 
 void Groups::groupKick(Group* group, EntityRef ref) {
 
+    if (group == nullptr)
+        return;
+
     // if you are the group leader, destroy your own group and kick everybody
     if (group->members[0] == ref) {
         disbandGroup(group);
diff --git a/src/Missions.cpp b/src/Missions.cpp
index b13699a..7bbdba5 100644
--- a/src/Missions.cpp
+++ b/src/Missions.cpp
@@ -386,6 +386,9 @@ static void taskStart(CNSocket* sock, CNPacketData* data) {
 static void taskEnd(CNSocket* sock, CNPacketData* data) {
     sP_CL2FE_REQ_PC_TASK_END* missionData = (sP_CL2FE_REQ_PC_TASK_END*)data->buf;
 
+    if (Missions::Tasks.find(missionData->iTaskNum) == Missions::Tasks.end())
+        return;
+
     TaskData* task = Missions::Tasks[missionData->iTaskNum];
 
     // handle timed mission failure
diff --git a/src/Nanos.cpp b/src/Nanos.cpp
index 8fa9629..73082be 100644
--- a/src/Nanos.cpp
+++ b/src/Nanos.cpp
@@ -110,7 +110,7 @@ void Nanos::summonNano(CNSocket *sock, int slot, bool silent) {
 }
 
 static void setNanoSkill(CNSocket* sock, sP_CL2FE_REQ_NANO_TUNE* skill) {
-    if (skill->iNanoID >= NANO_COUNT)
+    if (skill == nullptr || skill->iNanoID >= NANO_COUNT || skill->iNanoID < 0)
         return;
 
     Player *plr = PlayerManager::getPlayer(sock);