For usages of assert() that are meant to persist in Release builds (when NDEBUG is defined), replace those usages with persistent alternatives

src/staticobject.h

@@ -68,8 +68,7 @@ public:
 			{
 				dstream<<"ERROR: StaticObjectList::insert(): "
 						<<"id already exists"<<std::endl;
-				assert(0);
-				return;
+				FATAL_ERROR("StaticObjectList::insert()");
 			}
 			m_active[id] = obj;
 		}
@@ -77,7 +76,7 @@ public:
 
 	void remove(u16 id)
 	{
-		assert(id != 0);
+		assert(id != 0); // Pre-condition
 		if(m_active.find(id) == m_active.end())
 		{
 			dstream<<"WARNING: StaticObjectList::remove(): id="<<id