Format specifier '%s'

The application crashed with Proguard in the Release build.
Debug build works correctly.
The Crash relates to the following method.

HtmlParser() {
    XmlPullParser xmlPullParser = null;

    try {
        final XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
        factory.setValidating(false);
        factory.setFeature(Xml.FEATURE_RELAXED, true);
        xmlPullParser = factory.newPullParser();
    } catch (XmlPullParserException e) {
        Logger.w(RequestActivity.LOG_TAG, "Unable to parse rich text. Error: '%s' | '%s'", e
                .getLocalizedMessage());
    } finally {
        xpp = xmlPullParser;
    }
}

The application crashed in the catch block in the following case of the formatter class.

case 0:  // ordinary index
    lasto++;
    last = lasto;
    if (args != null && lasto > args.length - 1)
        throw new MissingFormatArgumentException(fs.toString());
    fs.print((args == null ? null : args[lasto]), l);
    break;

I'm using the following proguard rules.

-keep class zendesk.** { *; }
-keepnames class zendesk.** { *; }
-keepnames class okhttp3.internal.publicsuffix.PublicSuffixDatabase