pica: Move mutex lock below tracing check on register write (#210)

Co-authored-by: IndecisiveTurtle <47210458+raphaelthegreat@users.noreply.github.com>

src/video_core/debug_utils/debug_utils.cpp

@@ -272,11 +272,11 @@ void StartPicaTracing() {
 }
 
 void OnPicaRegWrite(u16 cmd_id, u16 mask, u32 value) {
-    std::lock_guard lock(pica_trace_mutex);
-
     if (!g_is_pica_tracing)
         return;
 
+    std::lock_guard lock(pica_trace_mutex);
+
     pica_trace->writes.push_back(PicaTrace::Write{cmd_id, mask, value});
 }