adding block.basefee only if there us baseFeePerGas available

libs/remix-ui/debugger-ui/src/lib/vm-debugger/global-variables.tsx

@@ -5,7 +5,6 @@ import { BN } from 'ethereumjs-util'
 export const GlobalVariables = ({ block, receipt, tx }) => {
   // see https://docs.soliditylang.org/en/latest/units-and-global-variables.html#block-and-transaction-properties
   const globals = {
-    'block.basefee': (new BN(block.baseFeePerGas.replace('0x', ''), 'hex')).toString(10) + ` Wei (${block.baseFeePerGas})`,
     'block.chainid': tx.chainId,
     'block.coinbase': block.miner,
     'block.difficulty': block.difficulty,
@@ -17,6 +16,9 @@ export const GlobalVariables = ({ block, receipt, tx }) => {
     'msg.value': tx.value + ' Wei',
     'tx.origin': tx.from
   }
+  if (block.baseFeePerGas)
+    globals['block.basefee'] = (new BN(block.baseFeePerGas.replace('0x', ''), 'hex')).toString(10) + ` Wei (${block.baseFeePerGas})`
+
   return (
     <div id='globalvariable' data-id='globalvariable'>
       <DropdownPanel hexHighlight={false} bodyStyle={{ fontFamily: 'monospace' }} dropdownName='Global Variables' calldata={globals || {}} />