qspibus: fix begin_transaction() consistency and regenerate .pot

- Align begin_transaction() with bus_free() by delegating to it, so
  transfer_in_progress and has_pending_command are checked before
  entering a transaction. This prevents silently discarding a staged
  write_command() or starting a transaction during active DMA.
- Regenerate locale/circuitpython.pot to remove stale "Data buffer is
  null" entry left over from the previous round of error message reuse.

Author: ppsx

locale/circuitpython.pot

@@ -711,7 +711,6 @@ msgid "Buffer too short by %d bytes"
 msgstr ""
 
 #: ports/cxd56/common-hal/camera/Camera.c
-#: ports/espressif/common-hal/qspibus/QSPIBus.c
 #: shared-bindings/busdisplay/BusDisplay.c
 #: shared-bindings/framebufferio/FramebufferDisplay.c
 #: shared-bindings/struct/__init__.c shared-module/struct/__init__.c
@@ -874,8 +873,7 @@ msgstr ""
 msgid "Coordinate arrays types have different sizes"
 msgstr ""
 
-#: shared-module/usb/core/Device.c
-#: ports/espressif/common-hal/qspibus/QSPIBus.c
+#: ports/espressif/common-hal/qspibus/QSPIBus.c shared-module/usb/core/Device.c
 msgid "Could not allocate DMA capable buffer"
 msgstr ""
 
@@ -917,10 +915,6 @@ msgstr ""
 msgid "Data 0 pin must be byte aligned"
 msgstr ""
 
-#: ports/espressif/common-hal/qspibus/QSPIBus.c
-msgid "Data buffer is null"
-msgstr ""
-
 #: shared-module/jpegio/JpegDecoder.c
 msgid "Data format error (may be broken data)"
 msgstr ""
@@ -1536,7 +1530,7 @@ msgstr ""
 #: ports/stm/common-hal/busio/UART.c shared-bindings/fourwire/FourWire.c
 #: shared-bindings/i2cdisplaybus/I2CDisplayBus.c
 #: shared-bindings/paralleldisplaybus/ParallelBus.c
-#: shared-module/bitbangio/SPI.c
+#: shared-bindings/qspibus/QSPIBus.c shared-module/bitbangio/SPI.c
 msgid "No %q pin"
 msgstr ""
 

ports/espressif/common-hal/qspibus/QSPIBus.c

@@ -506,12 +506,10 @@ bool common_hal_qspibus_qspibus_bus_free(mp_obj_t obj) {
 
 bool common_hal_qspibus_qspibus_begin_transaction(mp_obj_t obj) {
     qspibus_qspibus_obj_t *self = MP_OBJ_TO_PTR(obj);
-    if (!self->bus_initialized || self->in_transaction) {
+    if (!common_hal_qspibus_qspibus_bus_free(obj)) {
         return false;
     }
     self->in_transaction = true;
-    self->has_pending_command = false;
-    self->pending_command = 0;
     return true;
 }