From 9dafb20273dda7e62b0b8f03651bb5204fc7360f Mon Sep 17 00:00:00 2001
From: Stefan Weil <sw@weilnetz.de>
Date: Fri, 8 Oct 2021 08:10:55 +0200
Subject: [PATCH] Fix TypeError on MacOS when lilypond was not found

This fixes a runtime error on MacOS when a user tries to build a preview
and the Lilypond installation was not found.

Traceback (most recent call last):
  [...]
  File "/Applications/Frescobaldi.app/Contents/Resources/lib/python3.9/frescobaldi_app/signals.py", line 308, in call
  File "/Applications/Frescobaldi.app/Contents/Resources/lib/python3.9/frescobaldi_app/cachedproperty.py", line 264, in checkstart
  File "/Applications/Frescobaldi.app/Contents/Resources/lib/python3.9/frescobaldi_app/cachedproperty.py", line 276, in run
  File "/Applications/Frescobaldi.app/Contents/Resources/lib/python3.9/frescobaldi_app/lilypondinfo.py", line 306, in frommacports
TypeError: unsupported operand type(s) for +: 'bool' and 'str'

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
 frescobaldi_app/lilypondinfo.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/frescobaldi_app/lilypondinfo.py b/frescobaldi_app/lilypondinfo.py
index 931c9bb56..868715348 100644
--- a/frescobaldi_app/lilypondinfo.py
+++ b/frescobaldi_app/lilypondinfo.py
@@ -301,7 +301,8 @@ def done():
     @CachedProperty.cachedproperty(depends=(abscommand, bindir))
     def frommacports(self):
         """Return True if this LilyPond is provided by MacPorts."""
-        if sys.platform.startswith('darwin'):
+        bindir = self.bindir()
+        if sys.platform.startswith('darwin') and bindir:
             import subprocess
             portbin = os.path.abspath(self.bindir() + '/port')
             if os.path.isfile(portbin) and os.access(portbin, os.X_OK):