create_dataframe not working for 15 minute interval

[dexterluu]

Bug
When trying to use the create_dataframe function to merge the load, temperature, and additional_variables dfs together with a 15-minute interval, it errors saying additional_variable_alignment not found.

To Reproduce
Steps to reproduce the behavior:

1. Call function 'create_dataframe' with a load, temperature, and additional_variables dataframe with the covert_to_data_interval option set to "15-min".
2. See error: Error in align.time.xts(., n = 60 * additional_variable_alignment) :
   object 'additional_variable_alignment' not found

Expected behavior
The expected behavior is to have all 3 dataframes merged.

Desktop (please complete the following information):

• OS: [e.g. Windows 10]
• R version [e.g. 4.2.1]