Avoid method not supported in Java 5.

Author: raphw

byte-buddy-agent/src/main/java/net/bytebuddy/agent/Attacher.java

@@ -65,7 +65,7 @@ public static void main(String[] args) {
         } catch (Throwable throwable) {
             try {
                 String property = System.getProperty(DUMP_PROPERTY);
-                if (property != null && !property.isEmpty()) {
+                if (property != null && property.length() > 0) {
                     PrintStream outputStream = new PrintStream(new FileOutputStream(property));
                     try {
                         throwable.printStackTrace(outputStream);