really fix saving

src/backends/gr.jl

@@ -1942,7 +1942,7 @@ for (mime, fmt) in (
         filepath = tempname() * "." * $fmt
         withenv(
             "GKS_ENCODING" => "utf8", 
-            "GKSwstype" => fmt, 
+            "GKSwstype" => $fmt, 
             "GKS_FILEPATH" => filepath
         ) do
             gr_display(plt, $fmt)
@@ -1966,9 +1966,10 @@ function _display(plt::Plot{GRBackend})
             rm(filepath)
         end
     else
-        ENV["GKS_DOUBLE_BUF"] = true
+        withenv("GKS_DOUBLE_BUF" => true) do
             gr_display(plt)
         end
     end
+end
 
 closeall(::GRBackend) = GR.emergencyclosegks()