Portfolio - When all exchanges are removed, getting KeyError causing select tokens to not work

[rapcmia]

Describe the bug

When testing portfolio, i remove all the exchanges from select exchanges and KeyError occurred causing select tokens to not work

Workaround: User can still refresh the page and will display again ✅

Steps to reproduce bug

1. Setup hummingbot/deploy with ./setup.sh
2. Add connectors on Credentials page
3. On Portfolio, click x on the Select Exchanges next Select Accounts
   • On Select Accounts, add your account again e.g master_account
   • Observed Select token does not display any of each connectors selected

[rapcmia]

Test: Adding a connector that has 0 balance
Most of the time it fails on my setup with same error reported

KeyError: 'value'
Traceback:
File "/home/dashboard/frontend/pages/orchestration/portfolio/app.py", line 190, in portfolio_overview
    total_balance_usd = round(portfolio_df["value"].sum(), 2)
                              ~~~~~~~~~~~~^^^^^^^^^
File "/opt/conda/envs/dashboard/lib/python3.12/site-packages/pandas/core/frame.py", line 4107, in __getitem__
    indexer = self.columns.get_loc(key)
              ^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/envs/dashboard/lib/python3.12/site-packages/pandas/core/indexes/range.py", line 417, in get_loc
    raise **KeyError(key)**

By default it should look like this (had to make few clicks on Select Exchange and refresh to work) ✅