Explicitly note which modifications in pixel history are unavailable

qrenderdoc/Windows/PixelHistoryView.cpp

@@ -476,6 +476,9 @@ private:
 
   QBrush backgroundBrush(const ModificationValue &val) const
   {
+    if(!val.IsValid())
+      return QBrush();
+
     float rangesize = (m_Display.rangeMax - m_Display.rangeMin);
 
     float r = val.col.floatValue[0];
@@ -521,6 +524,9 @@ private:
   {
     QString s;
 
+    if(!val.IsValid())
+      return tr("Unavailable");
+
     int numComps = (int)(m_Tex->format.compCount);
 
     if(forceComps > 0)