session: fix compilation when SESSION_DEBUG is on

Wrap SESSION_EVT in do loop to avoid complaints about if statement
having no arguments which can happen if debugging for groups is not
enabled.

Type: fix

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I35af179b806ed47a1e20816a19291c31fdb7566a
diff --git a/src/vnet/session/session_debug.h b/src/vnet/session/session_debug.h
index 45dd77c..d433ef4 100644
--- a/src/vnet/session/session_debug.h
+++ b/src/vnet/session/session_debug.h
@@ -396,9 +396,13 @@
 #define session_evt_grp_dbg_lvl(_evt)                                         \
   session_dbg_main.grp_dbg_lvl[session_evt_grp (_evt)]
 #define SESSION_EVT(_evt, _args...)                                           \
-  if (PREDICT_FALSE (session_evt_grp_dbg_lvl (_evt) >=                        \
-		     session_evt_lvl (_evt)))                                 \
-  CC (_evt, _HANDLER) (_args)
+  do                                                                          \
+    {                                                                         \
+      if (PREDICT_FALSE (session_evt_grp_dbg_lvl (_evt) >=                    \
+			 session_evt_lvl (_evt)))                             \
+	CC (_evt, _HANDLER) (_args);                                          \
+    }                                                                         \
+  while (0)
 #else
 #define SESSION_EVT(_evt, _args...)
 #define SESSION_DBG(_fmt, _args...)