code cleanup: there is no tyOptRef

compiler/jsgen.nim

@@ -194,14 +194,13 @@ proc mapType(typ: PType): TJSTypeKind =
      tyAnd, tyOr, tyNot, tyAnything, tyVoid:
     result = etyNone
   of tyGenericInst, tyInferred, tyAlias, tyUserTypeClass, tyUserTypeClassInst,
-     tySink:
+     tySink, tyOwned:
     result = mapType(typ.lastSon)
   of tyStatic:
     if t.n != nil: result = mapType(lastSon t)
     else: result = etyNone
   of tyProc: result = etyProc
   of tyCString: result = etyString
-  of tyOptAsRef: doAssert(false, "mapType")
 
 proc mapType(p: PProc; typ: PType): TJSTypeKind =
   result = mapType(typ)