reader.lua: re-order touchScreenProbe() after CanvasContext

Device:touchScreenProbe() may display some widget (on first
install on Kobo Touch), and needs CanvasContext initialized.
Prevent a crash in this case.

reader.lua

@@ -136,10 +136,6 @@ if Device:hasEinkScreen() then
         Device.screen:toggleSWDithering()
     end
 end
--- Touch screen
-if Device:needsTouchScreenProbe() then
-    Device:touchScreenProbe()
-end
 
 -- Handle global settings migration
 local SettingsMigration = require("ui/data/settings_migration")
@@ -149,6 +145,13 @@ SettingsMigration:migrateSettings(G_reader_settings)
 local CanvasContext = require("document/canvascontext")
 CanvasContext:init(Device)
 
+-- Touch screen (this may display some widget, on first install on Kobo Touch,
+-- so have it done after CanvasContext:init() but before Bidi.setup() to not
+-- have mirroring mess x/y probing).
+if Device:needsTouchScreenProbe() then
+    Device:touchScreenProbe()
+end
+
 -- UI mirroring for RTL languages, and text shaping configuration
 local Bidi = require("ui/bidi")
 Bidi.setup(lang_locale)