core: return empty perf stats before the system is running (#30)

The SDL frontend's title timer can fire before perf_stats exists and
crashed on its null mutex during boot.

Assisted-by: Claude (Anthropic)

Co-authored-by: givethesourceplox <272928635+givethesourceplox@users.noreply.github.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/core/core.cpp b/src/core/core.cpp
index 3728ccf8f7..64e1d8de06 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -496,6 +496,9 @@ struct System::Impl {
     }
 
     PerfStatsResults GetAndResetPerfStats() {
+        if (!perf_stats) {
+            return {};
+        }
         return perf_stats->GetAndResetStats(core_timing.GetGlobalTimeUs());
     }