Memory Corruption leads to Brain Damage

class VarTable
{
private:
    map<string, map<string, string>> itemsAttrs;

public:
    string itemGetAttr(const string& item, const string& attr) const
    {
        // Я не знаю STL, но считаю, что если тут что-то не найдено, кинется эксепшен
        return this->itemsAttrs.find(item)->second.find(attr)->second;
    }
};

#define assert_exception(expression)                                            \
{                                                                               \
    bool caughtException = false;                                               \
    try                                                                         \
    {                                                                           \
        expression;                                                             \
    }                                                                           \
    catch (...)                                                                 \
    {                                                                           \
        caughtException = true;                                                 \
    }                                                                           \
    if (caughtException)                                                        \
    {                                                                           \
        cout << #expression << " causes exception [OK]" << endl;                \
    }                                                                           \
    else                                                                        \
    {                                                                           \
        cout << #expression << " causes exception [FAIL]" << endl;              \
        exit(1);                                                                \
    }                                                                           \
}

VarTable variables;
variables.addItem("i");
assert(variables.hasItem("i"));
assert(!variables.itemHasAttr("i", "type"));
assert_exception(variables.itemGetAttr("i", "type"));

variables.hasItem("i") [OK]
!variables.itemHasAttr("i", "type") [OK]
variables.itemGetAttr("i", "type") causes exception [OK]

variables.itemSetAttr("i", "type", "int");

variables.hasItem("i") [OK]
!variables.itemHasAttr("i", "type") [OK]
variables.itemGetAttr("i", "type") causes exception [FAIL]