core/sd_salt: check if sd_salt is enabled before asking for SD card

core/src/apps/common/sd_salt.py

@@ -61,6 +61,9 @@ async def ensure_sd_card(ctx: wire.GenericContext) -> None:
 async def request_sd_salt(
     ctx: wire.GenericContext = wire.DUMMY_CONTEXT
 ) -> Optional[bytearray]:
+    if not storage.sd_salt.is_enabled():
+        return None
+
     while True:
         await ensure_sd_card(ctx)
         try: