Fix: Broken assert.

Patch applied from https://gist.github.com/LordAro/421dacee7b6911628849beaabc209f0c#file-0004-fix-broken-assert-patch

src/fios.cpp

@@ -77,7 +77,7 @@ void FileList::BuildFileList(AbstractFileType abstract_filetype, SaveLoadOperati
 {
 	this->Clear();
 
-	assert(fop == SLO_LOAD || SLO_SAVE);
+	assert(fop == SLO_LOAD || fop == SLO_SAVE);
 	switch (abstract_filetype) {
 		case FT_NONE:
 			break;