mCallback defined in BringYourOwnSection should be an object instead of a reference.

The referenced object could be destroyed and result in native crash when
mCallback is used.

Bug: 156536687
Test: manual test with registering a section from an app
Change-Id: Ie36c0e6e64be1246539f12999f037c24377686dd
diff --git a/cmds/incidentd/src/Section.h b/cmds/incidentd/src/Section.h
index 2ce45ed..bc4909d 100644
--- a/cmds/incidentd/src/Section.h
+++ b/cmds/incidentd/src/Section.h
@@ -207,7 +207,7 @@
     virtual status_t BlockingCall(unique_fd& pipeWriteFd) const;
 
 private:
-    const sp<IIncidentDumpCallback>& mCallback;
+    const sp<IIncidentDumpCallback> mCallback;
 };