Re #6547. Check that map has been fully filled.

Just checking that it's not empty can mean that filling it is in
progress, so we need to enter the critical block if that's the case.
This shouldn't have much (any?) performance implication as size(),
like empty(), takes constant time.

Code/Mantid/Framework/DataObjects/src/PeakColumn.cpp

@@ -28,7 +28,9 @@ namespace DataObjects
      */
     const std::string typeFromName(const std::string & name)
     {
-      if(TYPE_INDEX.empty())
+      // We should enter the critical section if the map has not been fully filled.
+      // Be sure to keep the value tested against in sync with the number of inserts below
+      if( TYPE_INDEX.size() != 17 )
       {
         PARALLEL_CRITICAL(fill_column_index_map)
         {
@@ -52,6 +54,7 @@ namespace DataObjects
             TYPE_INDEX.insert(std::make_pair("Col", "double"));
             TYPE_INDEX.insert(std::make_pair("QLab", "V3D"));
             TYPE_INDEX.insert(std::make_pair("QSample", "V3D"));
+            // If adding an entry, be sure to increment the size comparizon in the first line
           }
         }
       }