Merge pull request #74760 from lassade/unicode-err-uses-replacement-char

Don't append non unicode scalar values on the string, instead use the unicode replacement char

core/string/ustring.h

@@ -183,6 +183,7 @@ struct StrRange {
 class String {
 	CowData<char32_t> _cowdata;
 	static const char32_t _null;
+	static const char32_t _replacement_char;
 
 	void copy_from(const char *p_cstr);
 	void copy_from(const char *p_cstr, const int p_clip_to);