avcodec/wavpack: Fix leak and segfault on reallocation error

av_realloc_f() frees the buffer it is given on allocation
failure. But in this case, the buffer is an array of
ownership pointers, causing leaks on error. Furthermore,
the count of pointers is unchanged on error and the codec's
close function uses it to free said ownership pointers,
causing a NPD.
This is a regression since 46412a8935.

Fix this by switching to av_realloc_array().

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/wavpack.c

@@ -973,9 +973,11 @@ static inline int wv_unpack_mono(WavpackFrameContext *s, GetBitContext *gb,
 
 static av_cold int wv_alloc_frame_context(WavpackContext *c)
 {
-    c->fdec = av_realloc_f(c->fdec, c->fdec_num + 1, sizeof(*c->fdec));
-    if (!c->fdec)
+    WavpackFrameContext **fdec = av_realloc_array(c->fdec, c->fdec_num + 1, sizeof(*c->fdec));
+
+    if (!fdec)
         return -1;
+    c->fdec = fdec;
 
     c->fdec[c->fdec_num] = av_mallocz(sizeof(**c->fdec));
     if (!c->fdec[c->fdec_num])