lexe-ln: Return error when usable channels but max_sendable is 0

Author: lexe-agent

lexe-ln/src/command.rs

@@ -1603,10 +1603,6 @@ mod validate {
             ));
         }
 
-        if amount <= max_sendable {
-            return Ok(());
-        }
-
         // If they have a balance but not enough to exceed the channel reserve,
         // return a dedicated error message, instead of "cannot find route".
         if usable_lightning_balance > Amount::ZERO
@@ -1620,6 +1616,10 @@ mod validate {
             ));
         }
 
+        if amount <= max_sendable {
+            return Ok(());
+        }
+
         // Since we know the recipient, we can compute a more accurate maximum
         // sendable amount to this recipient (i.e. max flow) and expose that to
         // the user as a suggestion.