Merged in bugfix from mbed official (pull request ARMmbed#5942)

Author: AGlass0fMilk

rtos/TARGET_CORTEX/mbed_rtx_idle.cpp

@@ -179,7 +179,6 @@ static void default_idle_hook(void)
 
     core_util_critical_section_enter();
     uint32_t ticks_to_sleep = svcRtxKernelSuspend();
-    MBED_ASSERT(os_timer->get_tick() == svcRtxKernelGetTickCount());
     if (ticks_to_sleep) {
         os_timer->schedule_tick(ticks_to_sleep);