Fix using non-U nuclides in "Isotopics from peaks" tool when a non Sa…

…ndiaDecay data source is selected.

Fix bug where original data source specification was being used to get nuclide information, when should have been using one that had been corrected for the case where the nuclide wasnt a U nuclide.

Also added in a check to make sure the U-nuclide was in the specified dataset, and if not, fall-back to SandiaDecay.

src/RelActCalcManual.cpp

@@ -2366,9 +2366,50 @@ NucMatchResults fill_in_nuclide_info( const vector<RelActCalcManual::GenericPeak
 
     iso = nuc ? nuc->symbol : rctn->name();
 
+    // Make sure we try to use a U-data source, only for U, and the nuclides of it we have,
+    //  otherwise we'll default back to using SandiaDecay
     auto src = nuc_data_src;
     if( (nuc && (nuc->atomicNumber != 92)) || rctn )
+    {
       src = NucDataSrc::SandiaDecay;
+    }else if( nuc->atomicNumber == 92 )
+    {
+      auto has_U_nuc = [db]( const SandiaDecay::Nuclide *nuc, const vector<NuclideInfo> &input ) -> bool {
+        for( const NuclideInfo &inputnuc : input )
+        {
+          const SandiaDecay::Nuclide *inputnuc_ptr = db->nuclide( inputnuc.parent );
+          assert( inputnuc_ptr );
+          if( inputnuc_ptr == nuc )
+            return true;
+        }//for( const NuclideInfo &inputnuc : input )
+        return false;
+      };//filter_for_nuc(...)
+
+      // TODO: we should probably give a warning that we are using SandiaDecay data if the
+      //       uranium dataset doesn't have this nuclide.
+      switch( src )
+      {
+        case NucDataSrc::Icrp107_U:
+          if( !has_U_nuc(nuc, icrp107) )
+            src = NucDataSrc::SandiaDecay;
+        break;
+
+        case NucDataSrc::Lanl_U:
+          if( !has_U_nuc(nuc, lanl) )
+            src = NucDataSrc::SandiaDecay;
+        break;
+
+        case NucDataSrc::IcrpLanlGadras_U:
+          if( !has_U_nuc(nuc, lanl_icrp_gad) )
+            src = NucDataSrc::SandiaDecay;
+        break;
+
+        case NucDataSrc::SandiaDecay:
+        case NucDataSrc::Undefined:
+          break;
+      }//switch( src )
+    }//if( non-U nuclide ) / else
+
 
     switch( src )
     {
@@ -2401,7 +2442,7 @@ NucMatchResults fill_in_nuclide_info( const vector<RelActCalcManual::GenericPeak
     };//filter_for_nuc(...)
 
 
-    switch( nuc_data_src )
+    switch( src )
     {
       case NucDataSrc::Icrp107_U:
       {