Fix more integrators

openmmapi/src/BrownianIntegrator.cpp

@@ -72,6 +72,8 @@ double BrownianIntegrator::computeKineticEnergy() {
 }
 
 void BrownianIntegrator::step(int steps) {
+    if (context == NULL)
+        throw OpenMMException("This Integrator is not bound to a context!");  
     for (int i = 0; i < steps; ++i) {
         context->updateContextState();
         context->calcForcesAndEnergy(true, false);

plugins/drude/openmmapi/src/DrudeLangevinIntegrator.cpp

@@ -89,6 +89,8 @@ double DrudeLangevinIntegrator::computeKineticEnergy() {
 }
 
 void DrudeLangevinIntegrator::step(int steps) {
+    if (context == NULL)
+        throw OpenMMException("This Integrator is not bound to a context!");    
     for (int i = 0; i < steps; ++i) {
         context->updateContextState();
         context->calcForcesAndEnergy(true, false);

plugins/drude/openmmapi/src/DrudeSCFIntegrator.cpp

@@ -86,6 +86,8 @@ double DrudeSCFIntegrator::computeKineticEnergy() {
 }
 
 void DrudeSCFIntegrator::step(int steps) {
+    if (context == NULL)
+        throw OpenMMException("This Integrator is not bound to a context!");    
     for (int i = 0; i < steps; ++i) {
         context->updateContextState();
         context->calcForcesAndEnergy(true, false);

plugins/rpmd/openmmapi/src/RPMDIntegrator.cpp

@@ -168,6 +168,8 @@ double RPMDIntegrator::computeKineticEnergy() {
 }
 
 void RPMDIntegrator::step(int steps) {
+    if (context == NULL)
+        throw OpenMMException("This Integrator is not bound to a context!");    
     if (!hasSetPosition) {
         // Initialize the positions from the context.