Selection Expand does not work with unsaved files

[jpgrosen]

Open Nova, Create a new File, Invoke Selection Expand shows the following in Extension Console

Text Tools[8:26:12.636000] Extension encountered an uncaught exception:
/Users/jp/Library/Application Support/Nova/Extensions/biati.texttools/Scripts/main.dist.js (Line 1.295, Column 38)
Error: Path argument must be a string
    @[native code]
    getExtension@file:///Users/jp/Library/Application%20Support/Nova/Extensions/biati.texttools/Scripts/main.dist.js:1295:38
    expand@file:///Users/jp/Library/Application%20Support/Nova/Extensions/biati.texttools/Scripts/main.dist.js:1309:38
    @file:///Users/jp/Library/Application%20Support/Nova/Extensions/biati.texttools/Scripts/main.dist.js:3891:20

Error comes from this

class SelectionExpander {
  getExtension(editor) {
    let filePath = editor.document.path;
    let extension = nova.path.extname(filePath).substring(1); ## Line 1.295 BOOM