Partially modified to use C++11 standard nullptr

Change-Id: I0542c47d1979235206005bf603822b6ea415f2da
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/widgets/doc/snippets/qstyleplugin/main.cpp

@@ -95,7 +95,7 @@ QStyle *MyStylePlugin::create(const QString &key)
     } else if (lcKey == "starbuster") {
         return new StarBusterStyle;
     }
-    return 0;
+    return nullptr;
 }
 //! [1]