Index: server/DataAccess.cpp
===================================================================
--- server/DataAccess.cpp	(revision 84f979765a7ac106e9b5cdd57c31ba57e0aaadc7)
+++ server/DataAccess.cpp	(revision 95d7add6df1adfdcec277b580d3914bcd0a2e3d3)
@@ -144,4 +144,9 @@
    ostringstream oss;
 
+   if (connection == NULL) {
+       cout << "Error: non database connection exists" << endl;
+       return -1;
+   }
+
    oss << "INSERT into " << table << " (" << columns << ") VALUES (" << values << ")";
    cout << "query: " << oss.str() << endl;
@@ -162,4 +167,9 @@
    ostringstream oss;
 
+   if (connection == NULL) {
+       cout << "Error: non database connection exists" << endl;
+       return -1;
+   }
+
    oss << "UPDATE " << table << " SET " << values << " WHERE " << where;
    cout << "query: " << oss.str() << endl;
@@ -179,4 +189,9 @@
    int query_state;
    ostringstream oss;
+
+   if (connection == NULL) {
+       cout << "Error: non database connection exists" << endl;
+       return NULL;
+   }
 
    oss << "SELECT * FROM " << table;