qtmux: atomsrecovery: Fix compilation problem

Fixes a compilation error due to unused function result.
diff --git a/gst/quicktime/atomsrecovery.c b/gst/quicktime/atomsrecovery.c
index 9e1ba67..907683e 100644
--- a/gst/quicktime/atomsrecovery.c
+++ b/gst/quicktime/atomsrecovery.c
@@ -1070,8 +1070,16 @@
 
   data = g_malloc (4096);
   while (!feof (mdatrf->file)) {
-    gint read = fread (data, 1, 4096, mdatrf->file);
-    fwrite (data, 1, read, outf);
+    gint read, write;
+
+    read = fread (data, 1, 4096, mdatrf->file);
+    write = fwrite (data, 1, read, outf);
+
+    if (write != read) {
+      g_set_error (err, ATOMS_RECOV_QUARK, ATOMS_RECOV_ERR_FILE,
+          "Failed to copy data to output file: %s", g_strerror (errno));
+      goto fail;
+    }
   }
   g_free (data);