fix: fix incorrect string comparison in OPERATOR_ADDRESS check

Author: hexcow

scripts/fund_operator_devnet.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 # Check that OPERATOR_ADDRESS is not empty
-if [[ "$OPERATOR_ADDRESS" -eq "" ]]; then
+if [[ -z "$OPERATOR_ADDRESS" ]]; then
   echo "OPERATOR_ADDRESS is empty, using default value 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266"
   OPERATOR_ADDRESS=0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
 fi;