NIL is not of type REAL during x86 emission (valid code)

[Paul F. Dietz]

(lambda (x) (unless x (symbol-value x)))

===>

The value
  NIL
is not of type
  REAL
   [Condition of type TYPE-ERROR]
[...]
  0: ((LABELS SB-X86-64-ASM::IF-HI :IN SB-X86-64-ASM::MAYBE-EMIT-REX-PREFIX) #<SB-C:TN 'NIL!1 :CONSTANT>)
  1: (SB-X86-64-ASM::MAYBE-EMIT-REX-PREFIX #<SB-ASSEM:SEGMENT :TYPE :REGULAR> :DWORD #<SB-C:TN t2[EAX] :NORMAL> NIL #<SB-C:TN 'NIL!1 :CONSTANT>)
  2: (SB-X86-64-ASM::MOV #<SB-C:TN t2[EAX] :NORMAL> #<SB-X86-64-ASM::EA :DWORD base=#<SB-C:TN 'NIL!1 :CONSTANT> disp=-11>)
  3: (SB-VM::EMIT-SYMEVAL #<SB-C:TN t3[RDX] :NORMAL> #<SB-C:TN 'NIL!1 :CONSTANT> #<SB-C:TN t4[RAX] :NORMAL> T #<SB-C::VOP :INFO SYMBOL-VALUE :ARGS #<SB-C:TN-REF :TN #<SB-C:TN 'NIL!1 :CONSTANT> :WRITE-P NIL..
  4: ((SB-C::VOP SYMBOL-VALUE) #<SB-C::VOP :INFO SYMBOL-VALUE :ARGS #<SB-C:TN-REF :TN #<SB-C:TN 'NIL!1 :CONSTANT> :WRITE-P NIL :VOP SYMBOL-VALUE> :RESULTS #<SB-C:TN-REF :TN #<SB-C:TN t3[RDX] :NORMAL> :WRIT..
  5: (SB-C::GENERATE-CODE #<SB-C:COMPONENT :NAME (LAMBDA (X)) {10081F0A03}>)
  6: (SB-C::%COMPILE-COMPONENT #<SB-C:COMPONENT :NAME (LAMBDA (X)) {10081F0A03}>)
[...]

[Stas Boukarev (stassats)]

10dc2594647948554455a5ebd43a33e751bbaac0