Bug#45288: pb2 returns a lot of compilation warnings

sql/sql_lex.h:1437: warning: control reaches end of non-void function

sql/sql_lex.h

@@ -1389,6 +1389,7 @@ public:
     STMT_ACCESS_TABLE_COUNT
   };
 
+#ifndef DBUG_OFF
   static inline const char *stmt_accessed_table_string(enum_stmt_accessed_table accessed_table)
   {
     switch (accessed_table)
@@ -1422,7 +1423,10 @@ public:
         DBUG_ASSERT(0);
       break;
     }
+    MY_ASSERT_UNREACHABLE();
+    return "";
   }
+#endif  /* DBUG */
                
   #define BINLOG_DIRECT_ON 0xF0    /* unsafe when
                                       --binlog-direct-non-trans-updates