wallet_db upgrade: fix possible corruption of invoice amounts

see https://github.com/spesmilo/electrum/pull/7774

electrum/wallet.py

@@ -943,6 +943,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
                 amount_msat = '!'
                 break
             else:
+                assert isinstance(x.value, int), f"{x.value!r}"
                 amount_msat += x.value * 1000
         timestamp = None
         exp = None
@@ -2439,6 +2440,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
     def create_request(self, amount_sat: int, message: str, exp_delay: int, address: str):
         # for receiving
         amount_sat = amount_sat or 0
+        assert isinstance(amount_sat, int), f"{amount_sat!r}"
         exp_delay = exp_delay or 0
         timestamp = int(time.time())
         fallback_address = address if self.config.get('bolt11_fallback', True) else None

electrum/wallet_db.py

@@ -52,7 +52,7 @@ if TYPE_CHECKING:
 
 OLD_SEED_VERSION = 4        # electrum versions < 2.0
 NEW_SEED_VERSION = 11       # electrum versions >= 2.0
-FINAL_SEED_VERSION = 47     # electrum >= 2.7 will set this to prevent
+FINAL_SEED_VERSION = 48     # electrum >= 2.7 will set this to prevent
                             # old versions from overwriting new format
 
 
@@ -196,6 +196,7 @@ class WalletDB(JsonDB):
         self._convert_version_45()
         self._convert_version_46()
         self._convert_version_47()
+        self._convert_version_48()
         self.put('seed_version', FINAL_SEED_VERSION)  # just to be sure
 
         self._after_upgrade_tasks()
@@ -942,6 +943,16 @@ class WalletDB(JsonDB):
                     del requests[key]
         self.data['seed_version'] = 47
 
+    def _convert_version_48(self):
+        # fix possible corruption of invoice amounts, see #7774
+        if not self._is_upgrade_method_needed(47, 47):
+            return
+        invoices = self.data.get('invoices', {})
+        for key, item in list(invoices.items()):
+            if item['amount_msat'] == 1000 * "!":
+                item['amount_msat'] = "!"
+        self.data['seed_version'] = 48
+
     def _convert_imported(self):
         if not self._is_upgrade_method_needed(0, 13):
             return