Adding a block so that if there's not an activeBlockTemplate the system will kick out the miner to avoid the system crashing on reboot/startup.

lib/pool.js

@@ -292,6 +292,10 @@ function Miner(id, login, pass, ipAddress, startingDiff, messageSender, protoVer
         this.error = "Exchange addresses need payment IDs";
         this.valid_miner = false;
     }
+    if (!activeBlockTemplate){
+        this.error = "No active block template";
+        this.valid_miner = false;
+    }
 
     this.id = id;
     this.ipAddress = ipAddress;