mips/loongson_1b: install NULL handler is OK

libcpu/mips/loongson_1b/interrupt.c

@@ -104,15 +104,12 @@ rt_isr_handler_t rt_hw_interrupt_install(int vector, rt_isr_handler_t handler,
 	{
         old_handler = irq_handle_table[vector].handler;
 
-        if (handler != RT_NULL)
-        {
 #ifdef RT_USING_INTERRUPT_INFO
         rt_strncpy(irq_handle_table[vector].name, name, RT_NAME_MAX);
 #endif /* RT_USING_INTERRUPT_INFO */
         irq_handle_table[vector].handler = handler;
         irq_handle_table[vector].param = param;
     }
-    }
 
     return old_handler;
 }