renderer: mutex around color context creation/retrieval

app/render/renderer.cpp

@@ -75,6 +75,8 @@ void Renderer::Destroy()
 
 bool Renderer::GetColorContext(ColorProcessorPtr color_processor, Renderer::ColorContext *ctx)
 {
+  QMutexLocker locker(&color_cache_mutex_);
+
   ColorContext& color_ctx = *ctx;
 
   if (color_cache_.contains(color_processor->id())) {

app/render/renderer.h

@@ -125,6 +125,8 @@ private:
 
   QHash<QString, ColorContext> color_cache_;
 
+  QMutex color_cache_mutex_;
+
 };
 
 }