Improve error handling and improved handling of the .env file (which was currently unused)

[arsaboo]

Addressed some of the errors that I encountered:

$:~/ai-hedge-fund$ poetry run python src/agents.py --ticker AAPL
Traceback (most recent call last):
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 751, in <module>
    result = run_hedge_fund(
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 678, in run_hedge_fund
    final_state = app.invoke(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/__init__.py", line 1929, in invoke
    for chunk in self.stream(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/__init__.py", line 1649, in stream
    for _ in runner.tick(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/runner.py", line 105, in tick
    run_with_retry(t, retry_policy, writer=writer)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/retry.py", line 44, in run_with_retry
    task.proc.invoke(task.input, config)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/utils/runnable.py", line 410, in invoke
    input = context.run(step.invoke, input, config, **kwargs)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/utils/runnable.py", line 184, in invoke
    ret = context.run(self.func, input, **kwargs)
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 46, in market_data_agent
    prices = get_prices(
  File "/home/arsaboo/ai-hedge-fund/src/tools.py", line 125, in get_prices
    raise Exception(
Exception: Error fetching data: 402 - {"error":"Insufficient credits","message":"Your current balance is $0.00. Please add more credits to continue using the API."}

$:~/ai-hedge-fund$ poetry run python src/agents.py --ticker AAPL
Traceback (most recent call last):
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 751, in <module>
    result = run_hedge_fund(
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 678, in run_hedge_fund
    final_state = app.invoke(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/__init__.py", line 1929, in invoke
    for chunk in self.stream(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/__init__.py", line 1649, in stream
    for _ in runner.tick(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/runner.py", line 160, in tick
    _panic_or_proceed(
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/runner.py", line 370, in _panic_or_proceed
    raise exc
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/executor.py", line 70, in done
    task.result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 451, in result
    return self.__get_result()
  File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
    raise self._exception
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/pregel/retry.py", line 44, in run_with_retry
    task.proc.invoke(task.input, config)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/utils/runnable.py", line 410, in invoke
    input = context.run(step.invoke, input, config, **kwargs)
  File "/home/arsaboo/.cache/pypoetry/virtualenvs/ai-hedge-fund-2IwyPuRU-py3.10/lib/python3.10/site-packages/langgraph/utils/runnable.py", line 184, in invoke
    ret = context.run(self.func, input, **kwargs)
  File "/home/arsaboo/ai-hedge-fund/src/agents.py", line 357, in sentiment_agent
    if trade["transaction_shares"] < 0:
TypeError: '<' not supported between instances of 'NoneType' and 'int'