hal: Fix a pointer deference issue

- For HFP client usecase active input is not
  updated with current input stream which results
  in issue. To avoid check for active_input value
  before deferencing.
  
Change-Id: I080bf4bf6f069ef6f7a182f5a1542066503ca09c
diff --git a/hal/msm8974/platform.c b/hal/msm8974/platform.c
index f5aa3c4..5b04d17 100644
--- a/hal/msm8974/platform.c
+++ b/hal/msm8974/platform.c
@@ -8400,7 +8400,7 @@
     } else if (my_data->is_internal_codec && !audio_is_usb_in_device(snd_device)) {
         sample_rate =  CODEC_BACKEND_DEFAULT_SAMPLE_RATE;
         channels = CODEC_BACKEND_DEFAULT_TX_CHANNELS;
-        if (adev->active_input->bit_width == 24)
+        if (adev->active_input && adev->active_input->bit_width == 24)
             bit_width = platform_get_snd_device_bit_width(snd_device);
     } else {
         struct listnode *node;