qt init: on exc, let crash reporter appear instead of silently dying

related: https://github.com/spesmilo/electrum/issues/7390

```
20210706T091826.513398Z |    ERROR | __main__ | daemon.run_gui errored
Traceback (most recent call last):
  File "run_electrum", line 407, in handle_cmd
  File "electrum\daemon.py", line 584, in run_gui
  File "electrum\gui\qt\__init__.py", line 414, in main
  File "electrum\gui\qt\__init__.py", line 291, in wrapper
  File "electrum\gui\qt\__init__.py", line 316, in start_new_window
  File "electrum\gui\qt\__init__.py", line 361, in _start_wizard_to_select_or_create_wallet
  File "electrum\wallet_db.py", line 73, in __init__
  File "electrum\wallet_db.py", line 106, in load_data
  File "electrum\util.py", line 412, in <lambda>
  File "electrum\util.py", line 408, in do_profile
  File "electrum\wallet_db.py", line 175, in upgrade
  File "electrum\wallet_db.py", line 540, in _convert_version_24
ValueError: too many values to unpack (expected 2)
```

electrum/gui/qt/__init__.py

@@ -45,7 +45,7 @@ import PyQt5.QtCore as QtCore
 from electrum.i18n import _, set_language
 from electrum.plugin import run_hook
 from electrum.base_wizard import GoBack
-from electrum.util import (UserCancelled, profiler,
+from electrum.util import (UserCancelled, profiler, send_exception_to_crash_reporter,
                            WalletFileException, BitcoinException, get_new_wallet_name)
 from electrum.wallet import Wallet, Abstract_Wallet
 from electrum.wallet_db import WalletDB
@@ -58,6 +58,7 @@ from .network_dialog import NetworkDialog
 from .stylesheet_patcher import patch_qt_stylesheet
 from .lightning_dialog import LightningDialog
 from .watchtower_dialog import WatchtowerDialog
+from .exception_window import Exception_Hook
 
 if TYPE_CHECKING:
     from electrum.daemon import Daemon
@@ -296,7 +297,7 @@ class ElectrumGui(Logger):
         return wrapper
 
     @count_wizards_in_progress
-    def start_new_window(self, path, uri, *, app_is_starting=False):
+    def start_new_window(self, path, uri, *, app_is_starting=False) -> Optional[ElectrumWindow]:
         '''Raises the window for the wallet if it is open.  Otherwise
         opens the wallet and creates a new window for it'''
         wallet = None
@@ -398,6 +399,8 @@ class ElectrumGui(Logger):
         self.app.lastWindowClosed.connect(self._maybe_quit_if_no_windows_open)
         self.app.aboutToQuit.connect(self._cleanup_before_exit)
         signal.signal(signal.SIGINT, lambda *args: self.app.quit())
+        # hook for crash reporter
+        Exception_Hook.maybe_setup(config=self.config)
         # first-start network-setup
         try:
             self.init_network()
@@ -411,11 +414,18 @@ class ElectrumGui(Logger):
         # start wizard to select/create wallet
         self.timer.start()
         path = self.config.get_wallet_path(use_gui_last_wallet=True)
-        if not self.start_new_window(path, self.config.get('url'), app_is_starting=True):
-            return
+        try:
+            if not self.start_new_window(path, self.config.get('url'), app_is_starting=True):
+                return
+        except Exception as e:
+            self.logger.error("error loading wallet (or creating window for it)")
+            send_exception_to_crash_reporter(e)
+            # Let Qt event loop start properly so that crash reporter window can appear.
+            # We will shutdown when the user closes that window, via lastWindowClosed signal.
         # main loop
+        self.logger.info("starting Qt main loop")
         self.app.exec_()
-        # on some platforms the exec_ call may not return, so use clean_up()
+        # on some platforms the exec_ call may not return, so use _cleanup_before_exit
 
     def stop(self):
         self.logger.info('closing GUI')

electrum/gui/qt/exception_window.py

@@ -174,12 +174,13 @@ class Exception_Hook(QObject, Logger):
         self._report_exception.connect(_show_window)
 
     @classmethod
-    def maybe_setup(cls, *, config: 'SimpleConfig', wallet: 'Abstract_Wallet') -> None:
+    def maybe_setup(cls, *, config: 'SimpleConfig', wallet: 'Abstract_Wallet' = None) -> None:
         if not config.get(BaseCrashReporter.config_key, default=True):
             return
         if not cls._INSTANCE:
             cls._INSTANCE = Exception_Hook(config=config)
-        cls._INSTANCE.wallet_types_seen.add(wallet.wallet_type)
+        if wallet:
+            cls._INSTANCE.wallet_types_seen.add(wallet.wallet_type)
 
     def handler(self, *exc_info):
         self.logger.error('exception caught by crash reporter', exc_info=exc_info)

electrum/gui/qt/main_window.py

@@ -185,7 +185,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         if wallet.has_lightning():
             self.wallet.config.set_key('show_channels_tab', True)
 
-        self.setup_exception_hook()
+        Exception_Hook.maybe_setup(config=self.config, wallet=self.wallet)
 
         self.network = gui_object.daemon.network  # type: Network
         self.fx = gui_object.daemon.fx  # type: FxThread
@@ -317,10 +317,6 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             self._update_check_thread.checked.connect(on_version_received)
             self._update_check_thread.start()
 
-    def setup_exception_hook(self):
-        Exception_Hook.maybe_setup(config=self.config,
-                                   wallet=self.wallet)
-
     def run_coroutine_from_thread(self, coro, on_result=None):
         def task():
             try: