GRID: more informative error message when looking for values outside the grid

[makedoc]

CHANGES/v2.2.txt

@@ -143,6 +143,8 @@ Version 2.2.3 ()
 For users:
 - Updated patch for gromacs 5.1.x to fix a problem when plumed was trying to write to an already
   closed gromacs log file.
+- When looking for a value outside the GRID now the error include the name of the responsible 
+  collective variable
 
 For developers:
 

src/tools/Grid.cpp

@@ -171,7 +171,7 @@ Grid::index_t Grid::getIndex(const vector<unsigned> & indices) const {
   if(indices[i]>=nbin_[i]) {
     std::string is;
     Tools::convert(i,is);
-    std::string msg="ERROR: the system is looking for a value outside the grid along the " + is;
+    std::string msg="ERROR: the system is looking for a value outside the grid along the " + is + " ("+getArgNames()[i]+")";
     plumed_merror(msg+" index!");
   }
  index_t index=indices[dimension_-1];