Fix WebLogic NPE (#1142)

Author: felixbarny

apm-agent-plugins/apm-servlet-plugin/src/main/java/co/elastic/apm/agent/servlet/ServletTransactionHelper.java

@@ -155,7 +155,11 @@ public static void setUsernameIfUnset(@Nullable String userName, TransactionCont
  @VisibleForAdvice
  public void onAfter(Transaction transaction, @Nullable Throwable exception, boolean committed, int status,
  boolean overrideStatusCodeOnThrowable, String method, @Nullable Map<String, String[]> parameterMap,
- String servletPath, @Nullable String pathInfo, @Nullable String contentTypeHeader, boolean deactivate) {
+ @Nullable String servletPath, @Nullable String pathInfo, @Nullable String contentTypeHeader, boolean deactivate) {
+ if (servletPath == null) {
+ // the servlet path is specified as non-null but WebLogic does return null...
+ servletPath = "";
+ }
  try {
  // thrown the first time a JSP is invoked in order to register it
  if (exception != null && "weblogic.servlet.jsp.AddToMapException".equals(exception.getClass().getName())) {