[sc-users] error when using .gui method on an Instr

["Jascha Narveson" <jnarveson@xxxxxxxxxxxx>]

I just downloaded a fresh UB of SC3 from the realizedsound site, and, out
of the box, tried to use .gui on an Intr, and got this:

ERROR: Primitive '_FileOpen' failed.
Wrong type.
RECEIVER:
Instance of File {    (1691B820, gc=54, fmt=00, flg=00, set=01)
  instance variables [1]
    fileptr : nil
}
CALL STACK:
	MethodError:reportError   169C1A90
		arg this = <instance of PrimitiveFailedError>
	Nil:handleError   169C2A50
		arg this = nil
		arg error = <instance of PrimitiveFailedError>
	Thread:handleError   169D3C10
		arg this = <instance of Thread>
		arg error = <instance of PrimitiveFailedError>
	Object:throw   169CC410
		arg this = <instance of PrimitiveFailedError>
	Object:primitiveFailed   169C2690
		arg this = <instance of File>
	File:open   169CDC10
		arg this = <instance of File>
		arg pathName = nil
		arg mode = "r"
	Meta_File:exists   169B8A80
		arg this = class File
		arg pathName = nil
		var file = nil
	Instr:guiBody   168EC330
		arg this = <instance of Instr>
		arg layout = <instance of FlowView>
		var defs = nil
		var tf = <instance of SCTextField>
		var source = "{ arg freq=440,int1=5,int2 =..."
		var lines = [*8]
		var h = 160
		var w = 680
	FlowView:flow   16900010
		arg this = <instance of FlowView>
		arg func = <instance of Function>
		arg bounds = nil
		var f = <instance of FlowView>
	ModelImplementsGuiBody:gui   169E8B60
		arg this = <instance of ModelImplementsGuiBody>
		arg lay = nil
		arg bounds = nil
		arg args = [*0]
		var layout = <instance of MultiPageLayout>
	Interpreter:interpretPrintCmdLine   169C8630
		arg this = <instance of Interpreter>
		var res = nil
		var func = <instance of Function>
	Process:interpretPrintCmdLine   169CCE30
		arg this = <instance of Main>