fix conflict between filesize and hexadecimal numbers (#9309)

closes #9278 

# Description

removes ambiguity between the `b` the filesize `bytes` unit and `b` the
hex digit

crates/nu-parser/src/parser.rs

@@ -2217,6 +2217,12 @@ pub fn parse_filesize(working_set: &mut StateWorkingSet, span: Span) -> Expressi
 
     let bytes = working_set.get_span_contents(span);
 
+    // the hex digit `b` might be mistaken for the unit `b`, so check that first
+    if bytes.starts_with(b"0x") {
+        working_set.error(ParseError::Expected("filesize with valid units", span));
+        return garbage(span);
+    }
+
     match parse_unit_value(bytes, span, FILESIZE_UNIT_GROUPS, Type::Filesize, |x| {
         x.to_uppercase()
     }) {