bricks/_common_stm32: Run pool hook on print if disconnected.

Fixes certain tight loops with f-strings locking up the hub when disconnected.

Fixes pybricks/support#1668

Author: laurensvalk

CHANGELOG.md

@@ -14,8 +14,10 @@
   from `3.6.0b1` to `3.5.0` and back to `3.6.0b1` ([support#1846]).
 - Fixed controls stopping if `use_gyro` is called again with the same
   argument as already active ([support#1858]).
+- Fixed lockup and reboot with f-strings in tight loops ([support#1668]).
 
 [support#1623]: https://github.com/pybricks/support/issues/1623
+[support#1668]: https://github.com/pybricks/support/issues/1668
 [support#1846]: https://github.com/pybricks/support/issues/1846
 [support#1858]: https://github.com/pybricks/support/issues/1858
 

bricks/_common_stm32/mphalport.c

@@ -138,13 +138,13 @@ void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
             continue;
         }
 
+        MICROPY_EVENT_POLL_HOOK
+
         if (err != PBIO_ERROR_AGAIN) {
             // Ignoring error for now. This means stdout lost if Bluetooth is
             // disconnected.
             return;
         }
-
-        MICROPY_EVENT_POLL_HOOK
     }
 }