Merge pull request #605 from peastman/master

Added a missing return statement

plugins/drude/openmmapi/src/DrudeForceImpl.cpp

@@ -143,6 +143,7 @@ void DrudeForceImpl::initialize(ContextImpl& context) {
 double DrudeForceImpl::calcForcesAndEnergy(ContextImpl& context, bool includeForces, bool includeEnergy, int groups) {
     if ((groups&(1<<owner.getForceGroup())) != 0)
         return kernel.getAs<CalcDrudeForceKernel>().execute(context, includeForces, includeEnergy);
+    return 0.0;
 }
 
 std::vector<std::string> DrudeForceImpl::getKernelNames() {