Fix when exporting spectrum files, and summing multiple records, but …

…only part of the file - an error was produced (something about invalid sample numbers).

The underlying cause was we were mapping the original sample numbers to instead start at 1, instead of whatever they previously did - but we werent updating the list of sample numbers that we wanted to sum, so the summing was throwning an error because some of the input sample numbers were not in the now re-numbered file.

src/ExportSpecFile.cpp

@@ -2987,12 +2987,14 @@ std::shared_ptr<const SpecMeas> ExportSpecFileTool::generateFileToSave()
       samples.erase( sample );
 
     // Now lets map sample numbers to 1 through N
+    samples.clear();
     int new_sample_number = 0;
     vector<pair<int,int>> old_to_new_samplenum;
     for( const int old_sample_number : answer->sample_numbers() )
     {
       ++new_sample_number;
       old_to_new_samplenum.emplace_back( old_sample_number, new_sample_number );
+      samples.insert( new_sample_number );
     }//for( loop over sample numbers )
 
     answer->change_sample_numbers( old_to_new_samplenum );