Let wxGetFileKind(FILE*) return wxFILE_KIND_UNKNOWN for NULL

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@35186 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/filefn.cpp

@@ -1968,7 +1968,7 @@ wxFileKind wxGetFileKind(FILE *fp)
     (void)fp;
     return wxFILE_KIND_DISK;
 #else
-    return wxGetFileKind(fileno(fp));
+    return fp ? wxGetFileKind(fileno(fp)) : wxFILE_KIND_UNKNOWN;
 #endif
 }