unix: handle edge case where path does not exist

fixes crash when passing an invalid path with the "-g" launch option
the algorithm would recurse up the tree infinitely looking for blank parent directories
probably fixes more things

src/Common/unix/FileStream_unix.cpp

@@ -7,6 +7,9 @@ fs::path findPathCI(const fs::path& path)
 
 	fs::path fName = path.filename();
 	fs::path parentPath = path.parent_path();
+	if (parentPath.empty())
+		return path;
+
 	if (!fs::exists(parentPath))
 	{
 		auto CIParent = findPathCI(parentPath);