Fix NUL bytes in UBJSON/BJData high-precision numbers (#5760)

* Fix NUL-terminated UBJSON and BJData high-precision payloads

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Use English comments for the high-precision NUL fix

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Track NUL bytes while reading high-precision payloads

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Drop dates from code comments.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Report a NUL in a high-precision number where it is read

Return the parse error from the read loop so the byte offset points at the NUL, and drop the separate check after lexing.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

* Use fixed text for the high-precision NUL error

2026-10-06: Use the known zero byte directly instead of formatting and concatenating it. Preserve the SAX token, error message, and byte offset.
Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

---------

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

include/nlohmann/detail/input/binary_reader.hpp

@@ -3249,6 +3249,12 @@ class binary_reader
             {
                 return false;
             }
+            // the lexer would stop at a NUL and accept the digits before it
+            if (JSON_HEDLEY_UNLIKELY(current == '\0'))
+            {
+                return sax->parse_error(chars_read, "00", parse_error::create(115, chars_read,
+                                        exception_message("invalid number text; last byte: 0x00", "high-precision number"), nullptr));
+            }
             number_vector.push_back(static_cast<char>(current));
         }