Move the size check to be the first thing checked in CFAllocatorCreate

This saves us a lot of work is size is 0

Author: AZero13

CoreFoundation/Base.subproj/CFBase.c

@@ -581,7 +581,9 @@ CFAllocatorRef CFAllocatorCreate(CFAllocatorRef allocator, CFAllocatorContext *c
 
 void *CFAllocatorAllocate(CFAllocatorRef allocator, CFIndex size, CFOptionFlags hint) {
     CFAllocatorAllocateCallBack allocateFunc;
-    void *newptr = NULL;
+    void *newptr;
+
+    if (0 == size) return NULL;
 
     if (NULL == allocator) {
 	allocator = __CFGetDefaultAllocator();
@@ -594,14 +596,13 @@ void *CFAllocatorAllocate(CFAllocatorRef allocator, CFIndex size, CFOptionFlags
 #else
     __CFGenericValidateType(allocator, _kCFRuntimeIDCFAllocator);
 #endif
-    if (0 == size) return NULL;
 #if TARGET_OS_MAC
     if (_CFTypeGetClass(allocator) != __CFISAForCFAllocator()) {	// malloc_zone_t *
 	return malloc_zone_malloc((malloc_zone_t *)allocator, size);
     }
 #endif
-    newptr = NULL;
     allocateFunc = __CFAllocatorGetAllocateFunction(&allocator->_context);
+    newptr = NULL;
     if (allocateFunc) {
         newptr = (void *)INVOKE_CALLBACK3(allocateFunc, size, hint, allocator->_context.info);
     }