Fix possible invalid memory accesses

Author: vincentlaucsb

include/internal/csv_row.cpp

@@ -197,6 +197,8 @@ namespace csv {
                 this->daddy->operator[](_i));
         else
             this->field = nullptr;
+
+        this->data = this->daddy->data;
     }
 
     CSV_INLINE CSVRow::iterator::reference CSVRow::iterator::operator*() const {

include/internal/csv_row.hpp

@@ -374,6 +374,7 @@ namespace csv {
 
         private:
             const CSVRow * daddy = nullptr;            // Pointer to parent
+            internals::RawCSVDataPtr data = nullptr;
             std::shared_ptr<CSVField> field = nullptr; // Current field pointed at
             int i = 0;                                 // Index of current field
         };