Gert,
The issue is that the strings.js that you copied from the ScaleBar widget is saying that there should be other language locale folders under the nls folder.
Open the strings.js file in the nls folder and delete these lines:
,
"ar": 1,
"cs": 1,
"da": 1,
"de": 1,
"el": 1,
"es": 1,
"et": 1,
"fi": 1,
"fr": 1,
"he": 1,
"it": 1,
"ja": 1,
"ko": 1,
"lt": 1,
"lv": 1,
"nb": 1,
"nl": 1,
"pl": 1,
"pt-br": 1,
"pt-pt": 1,
"ro": 1,
"ru": 1,
"sv": 1,
"th": 1,
"tr": 1,
"vi": 1,
"zh-cn": 1,
"zh-hk": 1,
"zh-tw": 1