LibJS/Bytecode: Make typeof return "undefined" on unresolvable IDs

Previously it would throw instead of returning "undefined" for
`typeof Identifier` if Identifier does not exist.

Userland/Libraries/LibJS/Bytecode/Instruction.h

@@ -82,6 +82,7 @@
     O(Sub)                           \
     O(Throw)                         \
     O(Typeof)                        \
+    O(TypeofVariable)                \
     O(UnaryMinus)                    \
     O(UnaryPlus)                     \
     O(UnsignedRightShift)            \