minor, replace nullptr checks with implicit ones

src/hb-subset-cff-common.cc

diff --git a/src/hb-subset-cff-common.cc b/src/hb-subset-cff-common.cc
index 1536c0d..04e1db2 100644
--- a/src/hb-subset-cff-common.cc
+++ b/src/hb-subset-cff-common.cc
@@ -158,7 +158,7 @@
 {
   TRACE_SERIALIZE (this);
   FDSELECT3_4 *p = c->allocate_size<FDSELECT3_4> (size);
-  if (unlikely (p == nullptr)) return_trace (false);
+  if (unlikely (!p)) return_trace (false);
   p->nRanges () = fdselect_ranges.length;
   for (unsigned int i = 0; i < fdselect_ranges.length; i++)
   {
@@ -184,7 +184,7 @@
 {
   TRACE_SERIALIZE (this);
   FDSelect *p = c->allocate_min<FDSelect> ();
-  if (unlikely (p == nullptr)) return_trace (false);
+  if (unlikely (!p)) return_trace (false);
   p->format = fdselect_format;
   size -= FDSelect::min_size;
 
@@ -194,7 +194,7 @@
   case 0:
   {
     FDSelect0 *p = c->allocate_size<FDSelect0> (size);
-    if (unlikely (p == nullptr)) return_trace (false);
+    if (unlikely (!p)) return_trace (false);
     unsigned int range_index = 0;
     unsigned int fd = fdselect_ranges[range_index++].code;
     for (unsigned int i = 0; i < num_glyphs; i++)