Use nullptr instead of 0 in call to FontConfig.

src/ports/SkFontConfigInterface_direct.cpp

Index: src/ports/SkFontConfigInterface_direct.cpp
diff --git a/src/ports/SkFontConfigInterface_direct.cpp b/src/ports/SkFontConfigInterface_direct.cpp
index d6fa96a46cfa5c418516a860edbfc9af9937a385..ccea794e1c76983ed3770439c7bf1094435b081a 100644
--- a/src/ports/SkFontConfigInterface_direct.cpp
+++ b/src/ports/SkFontConfigInterface_direct.cpp
@@ -632,7 +632,7 @@ bool SkFontConfigInterfaceDirect::matchFamilyName(const char familyName[],
     }
 
     FcResult result;
-    FcFontSet* font_set = FcFontSort(0, pattern, 0, 0, &result);
+    FcFontSet* font_set = FcFontSort(nullptr, pattern, 0, nullptr, &result);
     if (!font_set) {
         FcPatternDestroy(pattern);
         return false;