Fix @isdefined for globals

K"globalref" doesn't exist until later

Author: mlechu

src/closure_conversion.jl

@@ -338,7 +338,7 @@ function _convert_closures(ctx::ClosureConversionCtx, ex)
         elseif binfo.is_always_defined || is_self_captured(ctx, var)
             # Captured but unboxed vars are always defined
             @ast ctx ex true::K"Bool"
-        elseif kind(var) == K"globalref"
+        elseif binfo.kind == :global
             # Normal isdefined won't work for globals (#56985)
             @ast ctx ex [K"call"
                 "isdefinedglobal"::K"core"