Fix checking for NULL after usage

The pa_xmalloc calls oom() in case of NULL pointer returned by malloc() on one
hand and dereferencing of pointer is happen early than actual check on other
hand. Thus, just remove useless checks.

src/pulsecore/resampler.c

@@ -299,8 +299,7 @@ pa_resampler* pa_resampler_new(
     return r;
 
 fail:
-    if (r)
-        pa_xfree(r);
+    pa_xfree(r);
 
     return NULL;
 }