More clear message for character import failure

public/script.js

@@ -6838,6 +6838,11 @@ function importCharacter(file) {
         contentType: false,
         processData: false,
         success: async function (data) {
+            if (data.error) {
+                toastr.error('The file is likely invalid or corrupted.', 'Could not import character');
+                return;
+            }
+
             if (data.file_name !== undefined) {
                 $('#character_search_bar').val('').trigger('input');
                 $("#rm_info_block").transition({ opacity: 0, duration: 0 });