Don't ignore the result of fwrite. Since we're building with -Wall and -Werror, this causes compile failures.

testing/Messenger_test.c

@@ -138,7 +138,7 @@ int main(int argc, char *argv[])
         if ( file==NULL ){return 1;}
         uint8_t * buffer = malloc(Messenger_size());
         Messenger_save(buffer);
-        fwrite(buffer, 1, Messenger_size(), file);
+        size_t write_result = fwrite(buffer, 1, Messenger_size(), file);
         free(buffer);
         fclose(file);
     }