fix static_cast overflow in LocateAtom

An overflow would happen when the residue contains unknown atoms that
are not in the compound, and can prevent bonds from being properly
created in ConnectAtomsOfResidue.

modules/conop/src/processor.cc

@@ -327,10 +327,10 @@ void Processor::ReorderAtoms(mol::ResidueHandle residue,
   mol::impl::AtomImplList::iterator i=impl->GetAtomList().begin();
   for (; i!=impl->GetAtomList().end(); ++i) {
     mol::impl::AtomImplPtr atom=*i;
-    atom->SetState(std::numeric_limits<unsigned int>::max());
+    atom->SetState(std::numeric_limits<int>::max());
     int index=compound->GetAtomSpecIndex(atom->GetName());
     if (index==-1) {
-      atom->SetState(std::numeric_limits<unsigned int>::max());
+      atom->SetState(std::numeric_limits<int>::max());
       continue;
     }
     atom->SetState((compound->GetAtomSpecs())[index].ordinal);
@@ -350,7 +350,7 @@ bool Processor::HasUnknownAtoms(mol::ResidueHandle res,
   mol::AtomHandleList atoms=res.GetAtomList();
   for (mol::AtomHandleList::iterator 
        i=atoms.begin(), e=atoms.end(); i!=e; ++i) {
-    if ((*i).Impl()->GetState()==std::numeric_limits<unsigned int>::max()) {
+    if ((*i).Impl()->GetState()==std::numeric_limits<int>::max()) {
       if (((*i).GetElement()=="H" || (*i).GetElement()=="D") && 
           !strict_hydrogens) {
         continue;