fix crash when ACCEL_CHIP is an empty string

shaketune/measurement/vibrations_profile.py

@@ -20,6 +20,9 @@ def create_vibrations_profile(gcmd, config, st_process: ShakeTuneProcess) -> Non
     feedrate_travel = gcmd.get_float('TRAVEL_SPEED', default=120.0, minval=20.0)
     accel_chip = gcmd.get('ACCEL_CHIP', default=None)
 
+    if accel_chip == '':
+        accel_chip = None
+
     if (size / (max_speed / 60)) < 0.25:
         raise gcmd.error('The size of the movement is too small for the given speed! Increase SIZE or decrease MAX_SPEED!')
 

shaketune/post_processing/graph_vibrations.py

@@ -571,7 +571,7 @@ def plot_motor_config_txt(fig, motors, differences):
             for mot, lbl in motor_details
         ]
         config_blocks.append(
-            f'| TMC Autotune enabled (PWM freq target: X={motors[0].get_config("pwm_freq_target")}kHz / Y={motors[1].get_config("pwm_freq_target")}kHz)'
+            f'| TMC Autotune enabled (PWM freq target: X={int(motors[0].get_config("pwm_freq_target"))}kHz / Y={int(motors[1].get_config("pwm_freq_target"))}kHz)'
         )
     else:
         config_blocks = [