fixed handling missing diff attrs

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - osu: Fix panic on maps with 0 objects
 - Fixed timing point parsing on some (older) maps where "uninherited" value did not coincide with beat length
+- Fixed handling .osu files with missing difficulty attributes
 - Added `AttributeProvider` impl for `{Mode}PerformanceAttributes`
 - [BREAKING] Store `HitObject::sound` in `Beatmap::sounds` instead to reduce the struct size
 - [BREAKING] Removed the mode features `osu`, `fruits`, `taiko`, and `mania`. Now all modes are always supported.

src/parse/mod.rs

@@ -213,10 +213,12 @@ macro_rules! parse_difficulty_body {
             $buf.clear();
         }
 
-        $self.od = od.next_field("od")?;
-        $self.cs = cs.next_field("cs")?;
-        $self.hp = hp.next_field("hp")?;
-        $self.ar = ar.unwrap_or($self.od);
+        const DEFAULT_DIFFICULTY: f32 = 5.0;
+
+        $self.od = od.unwrap_or(DEFAULT_DIFFICULTY);
+        $self.cs = cs.unwrap_or(DEFAULT_DIFFICULTY);
+        $self.hp = hp.unwrap_or(DEFAULT_DIFFICULTY);
+        $self.ar = ar.unwrap_or(DEFAULT_DIFFICULTY);
         $self.slider_mult = sv.next_field("sv")?;
         $self.tick_rate = tick_rate.next_field("tick rate")?;