Changes handling of missing X-GitLab-Event header (#248).

src/main/java/org/gitlab4j/api/systemhooks/SystemHookManager.java

@@ -54,13 +54,19 @@ public class SystemHookManager extends HookManager {
      */
     public void handleEvent(HttpServletRequest request) throws GitLabApiException {
 
+        String eventName = request.getHeader("X-Gitlab-Event");
+        if (eventName == null || eventName.trim().isEmpty()) {
+            String message = "X-Gitlab-Event header is missing!";
+            LOGGER.warning(message);
+            return;
+        }
+
         if (!isValidSecretToken(request)) {
             String message = "X-Gitlab-Token mismatch!";
             LOGGER.warning(message);
             throw new GitLabApiException(message);
         }
 
-        String eventName = request.getHeader("X-Gitlab-Event");
         LOGGER.info("handleEvent: X-Gitlab-Event=" + eventName);
         if (!SYSTEM_HOOK_EVENT.equals(eventName)) {
             String message = "Unsupported X-Gitlab-Event, event Name=" + eventName;

src/main/java/org/gitlab4j/api/webhook/WebHookManager.java

@@ -52,13 +52,18 @@ public class WebHookManager extends HookManager {
      */
     public void handleEvent(HttpServletRequest request) throws GitLabApiException {
 
+        String eventName = request.getHeader("X-Gitlab-Event");
+        if (eventName == null || eventName.trim().isEmpty()) {
+            LOGGER.warning("X-Gitlab-Event header is missing!");
+            return;
+        }
+
         if (!isValidSecretToken(request)) {
             String message = "X-Gitlab-Token mismatch!";
             LOGGER.warning(message);
             throw new GitLabApiException(message);
         }
 
-        String eventName = request.getHeader("X-Gitlab-Event");
         LOGGER.info("handleEvent: X-Gitlab-Event=" + eventName);
         switch (eventName) {