Fix crash when handling clipboard data on macOS

[alexey-lysiuk]

Attempt to paste text that contains non-ASCII characters leads to a crash Depending on code path, it's a copy from null pointer or an unhandled exception

[sezero]

Is that @try{} @catch() {} a requirement of the old code?

[alexey-lysiuk]

I cannot say for such old versions of macOS, but actual versions need it as exception is thrown when conversion fails.

[sezero]

I guess [clipboardString cString] implies an actual conversion to ASCII?

And, no exception thrown for the new [clipboardString cStringUsingEncoding: NSASCIIStringEncoding] ?

[alexey-lysiuk]

Yes, "new" path returns NULL if conversion fails.

[sezero]

OK then.

For old targets: Instead of try/catch, would it be safe to do the following?

        if (! [clipboardString canBeConvertedToEncoding:NSASCIIStringEncoding])
            return NULL;
        srcdata = [clipboardString cString];

[alexey-lysiuk]

Replaced exception handling with check for possibility of conversion to ASCII.

[sezero]

The patch is in, thank you! And I also applied it to uhexen2 project.