Fix: get_historical_data returns warning and empty dataframe

[hkafrawi]

• Refactor: After a phrase is inputted that is not None but that city isnt found in get_historical_data, it returns a warning instead of an exception and an empty dataframe to avoid crashing the program.

Fixes #174 Resolves #174 Closes #174

[Milind220]

Will review this today - thanks for putting in the work!