Do not try to write to user dictionary if it cannot be opened

[Predelnik]

Fixes #363

[xomx]

I still think that you shouldn't left there a code using blindly a file handle without checking if the system call succeeded.
Maybe now it's ok for that R/O-case, but the _wfopen can fail also for other (not so obvious) reasons.

DSpellCheck/src/spellers/HunspellInterface.cpp

Lines 36 to 38 in a152beb

	auto fp = _wfopen(dictionary_path, L"a");
	fprintf(fp, "%s\n", word);
	fclose(fp);

[Predelnik]

Ok, thanks, I will add this check as well.