Fix selftest failures where empty 'profile' directory may not exist (eg git)

* SelfTestBase
    ...and make a tmp empty directory instead

engine/src/test/java/org/archive/crawler/selftest/SelfTestBase.java

@@ -89,6 +89,8 @@ public abstract class SelfTestBase extends TmpDirTestCase {
         File profileTemplate = new File(src, "profile");
         if(profileTemplate.exists()) {
             org.apache.commons.io.FileUtils.copyDirectory(profileTemplate, tmpDefProfile);
+        } else {
+            tmpDefProfile.mkdirs();
         }
         
         // Start up a Jetty that serves the selftest's content directory.