Feature fixes after PR review

- move step zero data test from colvarbias.cpp to ABF
- properly test for driven external parameter

Author: jhenin

src/colvar.cpp

@@ -2560,7 +2560,7 @@ std::string const colvar::get_state_params() const
      << "  x "
      << std::setprecision(cvm::cv_prec)
      << std::setw(cvm::cv_width);
-  if (is_enabled(f_cv_external)) {
+  if (is_enabled(f_cv_external) && is_enabled(f_cv_extended_Lagrangian)) {
     // For an external colvar, x is one timestep in the future after integration
     // write x at beginning of timestep
     os << x_reported << "\n";

src/colvarbias.cpp

@@ -100,11 +100,6 @@ int colvarbias::init(std::string const &conf)
     colvar_values[i].type(colvars[i]->value().type());
     colvar_forces[i].type(colvar_values[i].type());
     previous_colvar_forces[i].type(colvar_values[i].type());
-    if (!colvars[i]->is_enabled(f_cv_total_force_current_step)) {
-      // If any colvar does not have current-step total force, then
-      // we can't do step 0 data
-      feature_states[f_cvb_step_zero_data].available = false;
-    }
   }
 
   output_prefix = cvm::output_prefix();

src/colvarbias_abf.cpp

@@ -136,6 +136,12 @@ int colvarbias_abf::init(std::string const &conf)
       enable(f_cvb_extended);
     }
 
+    if (!colvars[i]->is_enabled(f_cv_total_force_current_step)) {
+      // If any colvar does not have current-step total force, then
+      // we can't do step 0 data
+      provide(f_cvb_step_zero_data, false);
+    }
+
     // Cannot mix and match coarse time steps with ABF because it gives
     // wrong total force averages - total force needs to be averaged over
     // every time step