fix: conditionally apply is_group filter in accounting dimension query

[ruchamahabal]

Employee is a treeview doctype (has is_tree enabled from #39126) but it does not have the is_group field. Depends on reports_to for linking. Handle the error
Query filter for accounting dimension fails due to this

Traceback (most recent call last):
  File "apps/frappe/frappe/app.py", line 110, in application
    response = frappe.api.handle(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/api/__init__.py", line 49, in handle
    data = endpoint(**arguments)
           ^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/api/v1.py", line 36, in handle_rpc_call
    return frappe.handler.handle()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/handler.py", line 49, in handle
    data = execute_cmd(cmd)
           ^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/handler.py", line 85, in execute_cmd
    return frappe.call(method, **frappe.form_dict)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/__init__.py", line 1716, in call
    return fn(*args, **newargs)
           ^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/utils/typing_validations.py", line 31, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/desk/search.py", line 47, in search_link
    results = search_widget(
              ^^^^^^^^^^^^^^
  File "apps/frappe/frappe/utils/typing_validations.py", line 31, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/desk/search.py", line 94, in search_widget
    return frappe.call(
           ^^^^^^^^^^^^
  File "apps/frappe/frappe/__init__.py", line 1716, in call
    return fn(*args, **newargs)
           ^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/utils/typing_validations.py", line 31, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/__init__.py", line 2458, in wrapper
    return fn(**kwargs)
           ^^^^^^^^^^^^
  File "apps/erpnext/erpnext/controllers/queries.py", line 692, in get_filtered_dimensions
    output = frappe.get_list(
             ^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/__init__.py", line 1980, in get_list
    return frappe.model.db_query.DatabaseQuery(doctype).execute(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/model/db_query.py", line 192, in execute
    result = self.build_and_run()
             ^^^^^^^^^^^^^^^^^^^^
  File "apps/frappe/frappe/model/db_query.py", line 233, in build_and_run
    return frappe.db.sql(
           ^^^^^^^^^^^^^^
  File "apps/frappe/frappe/database/database.py", line 234, in sql
    self._cursor.execute(query, values)
  File "env/lib/python3.11/site-packages/pymysql/cursors.py", line 153, in execute
    result = self._query(query)
             ^^^^^^^^^^^^^^^^^^
  File "env/lib/python3.11/site-packages/pymysql/cursors.py", line 322, in _query
    conn.query(q)
  File "env/lib/python3.11/site-packages/pymysql/connections.py", line 558, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "env/lib/python3.11/site-packages/pymysql/connections.py", line 822, in _read_query_result
    result.read()
  File "env/lib/python3.11/site-packages/pymysql/connections.py", line 1200, in read
    first_packet = self.connection._read_packet()
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "env/lib/python3.11/site-packages/pymysql/connections.py", line 772, in _read_packet
    packet.raise_for_error()
  File "env/lib/python3.11/site-packages/pymysql/protocol.py", line 221, in raise_for_error
    err.raise_mysql_exception(self._data)
  File "env/lib/python3.11/site-packages/pymysql/err.py", line 143, in raise_mysql_exception
    raise errorclass(errno, errval)
pymysql.err.OperationalError: (1054, "Unknown column 'tabEmployee.is_group' in 'where clause'")