bug: fix LookupError with AntminerOld

pyasic/miners/backends/antminer.py

@@ -598,6 +598,7 @@ class AntminerOld(CGMiner):
                 pass
 
         if rpc_stats is not None:
+            try:
                 board_offset = -1
                 boards = rpc_stats["STATS"]
                 if len(boards) > 1:
@@ -610,7 +611,9 @@ class AntminerOld(CGMiner):
                     if board_offset == -1:
                         board_offset = 1
 
-                for i in range(board_offset, board_offset + self.expected_hashboards):
+                    for i in range(
+                        board_offset, board_offset + self.expected_hashboards
+                    ):
                         hashboard = HashBoard(
                             slot=i - board_offset, expected_chips=self.expected_chips
                         )
@@ -636,6 +639,11 @@ class AntminerOld(CGMiner):
                         if (not chips) or (not chips > 0):
                             hashboard.missing = True
                         hashboards.append(hashboard)
+            except LookupError:
+                return [
+                    HashBoard(slot=i, expected_chips=self.expected_chips)
+                    for i in range(self.expected_hashboards)
+                ]
 
         return hashboards