使用pwm设备时出现错误error: 'else' without a previous 'if'

error: 'else' without a previous 'if'
../drivers/drv_pwm.c: In function 'drv_pwm_get':
../drivers/drv_pwm.c:203:5: error: 'else' without a previous 'if'
     else
     ^
../drivers/drv_pwm.c: In function 'drv_pwm_set':
../drivers/drv_pwm.c:248:1: error: 'else' without a previous 'if'
 else
 ^
arm-none-eabi-gcc "../drivers/drv_usbd.c"