Fix initialization of function NULL pointer.

src/namespace.c

@@ -38,7 +38,7 @@ static int activeNamespace = 0;
     { .func = (void (*)()) cdiStreamDefVlist_ },            \
     { .func = (void (*)()) cdiStreamWriteVar_ },            \
     { .func = (void (*)()) cdiStreamwriteVarChunk_ },       \
-    { .data = NULL },                                       \
+    { .func = (void (*)()) 0 },                             \
     { .func = (void (*)()) cdiStreamCloseDefaultDelegate }, \
     { .func = (void (*)()) cdiStreamDefTimestep_ }, \
     { .func = (void (*)()) cdiStreamSync_ },                \