Add missing values to a frequency table in R

Question

I have a list of the format

>count_temp
      Week freq
    1  00    1
    2  01    1
    3  02    1
    4  03    1
    5  10    1
    6  12    2
    7  14    1

In the Week column, some data is missing (Weeks 4,5,6 etc..). I want these missing values to be included in my table with the frequency value '0'.

I tried out the answer suggested in How to create missing values in table in R? but my levels for both the columns are completely different. Is there anyway to do this?