crash reporter: if disabled via config, make sure EEQueue is flushed

If the user had `config.get("show_crash_reporter")==False`, they would
never get to see excs collected via `send_exception_to_crash_reporter(exc)`.

E.g.:
```
E | gui.qt.ElectrumGui | error loading wallet (or creating window for it)
Traceback (most recent call last):
  File "/opt/electrum/electrum/gui/qt/__init__.py", line 433, in main
    if not self.start_new_window(path, self.config.get('url'), app_is_starting=True):
  File "/opt/electrum/electrum/gui/qt/__init__.py", line 307, in wrapper
    return func(self, *args, **kwargs)
  File "/opt/electrum/electrum/gui/qt/__init__.py", line 332, in start_new_window
    wallet = self._start_wizard_to_select_or_create_wallet(path)
  File "/opt/electrum/electrum/gui/qt/__init__.py", line 377, in _start_wizard_to_select_or_create_wallet
    db = WalletDB(storage.read(), manual_upgrades=False)
  File "/opt/electrum/electrum/wallet_db.py", line 73, in __init__
    self.load_data(raw)
  File "/opt/electrum/electrum/wallet_db.py", line 104, in load_data
    self._after_upgrade_tasks()
  File "/opt/electrum/electrum/wallet_db.py", line 202, in _after_upgrade_tasks
    self._load_transactions()
  File "/opt/electrum/electrum/util.py", line 439, in <lambda>
    return lambda *args, **kw_args: do_profile(args, kw_args)
  File "/opt/electrum/electrum/util.py", line 435, in do_profile
    o = func(*args, **kw_args)
  File "/opt/electrum/electrum/wallet_db.py", line 1310, in _load_transactions
    self.data = StoredDict(self.data, self, [])
  File "/opt/electrum/electrum/json_db.py", line 79, in __init__
    self.__setitem__(k, v)
  File "/opt/electrum/electrum/json_db.py", line 44, in wrapper
    return func(self, *args, **kwargs)
  File "/opt/electrum/electrum/json_db.py", line 97, in __setitem__
    v = self.db._convert_dict(self.path, key, v)
  File "/opt/electrum/electrum/wallet_db.py", line 1361, in _convert_dict
    v = dict((k, SwapData(**x)) for k, x in v.items())
```

electrum/base_crash_reporter.py

@@ -146,6 +146,7 @@ class EarlyExceptionsQueue:
 
     @classmethod
     def set_hook_as_ready(cls):
+        """Flush the queue and disable it for future exceptions."""
         if cls._is_exc_hook_ready:
             return
         cls._is_exc_hook_ready = True

electrum/gui/kivy/uix/dialogs/crash_reporter.py

@@ -180,6 +180,7 @@ class ExceptionHook(base.ExceptionHandler, Logger):
         Logger.__init__(self)
         self.main_window = main_window
         if not main_window.electrum_config.get(BaseCrashReporter.config_key, default=True):
+            EarlyExceptionsQueue.set_hook_as_ready()  # flush already queued exceptions
             return
         # For exceptions in Kivy:
         base.ExceptionManager.add_handler(self)

electrum/gui/qt/exception_window.py

@@ -177,6 +177,7 @@ class Exception_Hook(QObject, Logger):
     @classmethod
     def maybe_setup(cls, *, config: 'SimpleConfig', wallet: 'Abstract_Wallet' = None) -> None:
         if not config.get(BaseCrashReporter.config_key, default=True):
+            EarlyExceptionsQueue.set_hook_as_ready()  # flush already queued exceptions
             return
         if not cls._INSTANCE:
             cls._INSTANCE = Exception_Hook(config=config)