obs-ffmpeg: Close VAAPI device on vaInitialize fail

On some systems (eg. mine), VAAPI fails on vaInitialize. Valgrind was
able to spot that the device was not being closed, and it appears to
have been correct. This fixes a memory leak.

plugins/obs-ffmpeg/vaapi-utils.c

@@ -99,6 +99,7 @@ VADisplay vaapi_open_device(int *fd, const char *device_path,
 	if (va_status != VA_STATUS_SUCCESS) {
 		blog(LOG_ERROR, "VAAPI: Failed to initialize display in %s",
 		     func_name);
+		vaapi_close_device(fd, va_dpy);
 		return NULL;
 	}