schedrelease() don't schedule if current interrupt frame is NULL

kernel/syscall/sched.c

@@ -11,7 +11,9 @@ int32_t SYSCALL0(sys_schedrelease) {
   Proc *proc = PROCS.current;
   spinlock_release(&PROCS.spinlock);
 
+  if (INTR_CURRENT_FRAME != NULL) {
     proc_sched((void *)INTR_CURRENT_FRAME);
+  }
 
   return E_OK;
 }

user/tb/main.c

@@ -124,8 +124,6 @@ void do_mode_interactive(void) {
             uprintf(ANSIQ_SCR_CLR_ALL);
             goto begin;
             break;
-        } else {
-          schedrelease();
         }
 
         if (b == '\n') {
@@ -136,6 +134,8 @@ void do_mode_interactive(void) {
           linebuf[cursor++] = b;
           uprintf("%c", b);
         }
+      } else {
+        schedrelease();
       }
     }