Fix ui_write in apps/apps.c

It used the default UI reader as fallback instead of the UI writer.

Fixes #4147
Fixes #4195
Reviewed-by: NKurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/4198)

apps/apps.c

@@ -240,7 +240,7 @@ static int ui_write(UI *ui, UI_STRING *uis)
         }
     }
 
-    writer = UI_method_get_reader(ui_fallback_method);
+    writer = UI_method_get_writer(ui_fallback_method);
     if (writer)
         return writer(ui, uis);
     return 1;