handle correctly the case with no active channels

lnbits/nodes/base.py

@@ -68,6 +68,7 @@ class ChannelStats(BaseModel):
             if channel.state == ChannelState.ACTIVE
         ]
 
+        if len(active_channel_sizes) > 0:
             return cls(
                 counts=counts,
                 avg_size=int(sum(active_channel_sizes) / len(active_channel_sizes)),
@@ -75,6 +76,14 @@ class ChannelStats(BaseModel):
                 smallest_size=min(active_channel_sizes),
                 total_capacity=sum(active_channel_sizes),
             )
+        else:
+            return cls(
+                counts=counts,
+                avg_size=0,
+                biggest_size=0,
+                smallest_size=0,
+                total_capacity=0,
+            )
 
 
 class NodeFees(BaseModel):