`LineOf` incorrectly throws `NumberFormatException` for non-numeric `@line` in XMIR

Problem

LineOf throws an unhandled NumberFormatException when a hand-written/broken XMIR carries a non-numeric @line, taking down the whole Source.defects() run.

Root cause

src/main/java/org/eolang/lints/LineOf.java:39-41:

public static String value(final XML xml) {
    final String line;
    final Optional<String> attr = xml.xpath("@line").stream().findFirst();
    if (attr.isPresent()) {
        line = String.valueOf(Integer.parseInt(attr.get()));
    } else {
        line = "0";
    }
    return line;
}

The javadoc promises 0 only for an absent attribute. If @line is present but not an integer (malformed manual XMIR), Integer.parseInt throws NumberFormatException (unchecked), which escapes past the sole catch (IOException) in Source.defects() (src/main/java/org/eolang/lints/Source.java:104-118) and aborts the entire analysis.

LineOf is used by five hand-written lints: LtAsciiOnly.java:42, LtIncorrectUnlint.java:48, LtReservedName.java:54, LtSyntaxVersion.java:70, LtTestNotVerb.java:77.

Minimal example

new Source(new XMLDocument("<object><o name=\"x\" line=\"abc\"/></object>")).defects();
// throws NumberFormatException: For input string: "abc"

Expected behavior

A non-numeric @line should fall back to 0 (consistent with the rest of the codebase), or be reported as a controlled IllegalStateException — not an unhandled NumberFormatException from the public API.

Related

• LtByXsl.java:179-205 — the XSL path has a stricter lineno(); the Java path should be consistent.
• src/test/java/org/eolang/lints/LineOf.java has no dedicated test at all.

Start with src/main/java/org/eolang/lints/LineOf.java:39-41 and review how Source.defects() handles failures in src/main/java/org/eolang/lints/Source.java:104-118. Inspect the five lints that use LineOf, then add focused coverage under src/test/java/org/eolang/lints/LineOf.java for a non-numeric @line. Done means malformed XMIR no longer causes an unhandled NumberFormatException and the chosen controlled behavior is tested.