fix regression

nimbus/vm/interpreter_dispatch.nim

@@ -258,7 +258,7 @@ proc homesteadVM(computation: var BaseComputation) =
 
 proc updateOpcodeExec*(computation: var BaseComputation, fork: Fork) =
   case fork
-  of FkFrontier:
+  of FkFrontier..FkThawing:
     computation.opCodeExec = frontierVM
     computation.frontierVM()
   of FkHomestead..FkSpurious:

nimbus/vm/transaction_tracer.nim

@@ -115,14 +115,14 @@ proc traceOpCodeEnded*(tracer: var TransactionTracer, c: BaseComputation, op: Op
   trace "Op", json = j.pretty()
 
 proc traceError*(tracer: var TransactionTracer, c: BaseComputation) =
-  let j = tracer.trace["structLogs"].elems[^1]
+  if tracer.trace["structLogs"].elems.len > 0:
+    let j = tracer.trace["structLogs"].elems[^1]
+    j["error"] = %(c.error.info)
+    trace "Error", json = j.pretty()
 
   # TODO: figure out how to get gasCost
   # when contract execution failed before traceOpCodeEnded called
   # because exception raised
   #j["gasCost"] = %
 
-  j["error"] = %(c.error.info)
   tracer.trace["failed"] = %true
-
-  trace "Error", json = j.pretty()

tests/fixtures/TracerTests/block46402.json

@@ -704,7 +704,7 @@
           "0000000000000000000000000000000000000000000000000000000000000000",
           "0000000000000000000000000000000000000000000000000000000000000060"
         ],
-        "error": ""
+        "error": "Invalid instruction, received an opcode not implemented in the current fork."
       }
     ]
   },