avoid reporting negative memory allocation when memory_usage() is called before initialized

src/USER-TALLY/compute_force_tally.cpp

@@ -215,7 +215,7 @@ void ComputeForceTally::compute_peratom()
 
 double ComputeForceTally::memory_usage()
 {
-  double bytes = nmax*size_peratom_cols * sizeof(double);
+  double bytes = (nmax < 0) ? 0 : nmax*size_peratom_cols * sizeof(double);
   return bytes;
 }
 

src/USER-TALLY/compute_heat_flux_tally.cpp

@@ -275,7 +275,7 @@ void ComputeHeatFluxTally::compute_vector()
 
 double ComputeHeatFluxTally::memory_usage()
 {
-  double bytes = nmax*comm_reverse * sizeof(double);
+  double bytes = (nmax < 0) ? 0 : nmax*comm_reverse * sizeof(double);
   return bytes;
 }
 

src/USER-TALLY/compute_pe_tally.cpp

@@ -199,7 +199,7 @@ void ComputePETally::compute_peratom()
 
 double ComputePETally::memory_usage()
 {
-  double bytes = nmax*size_peratom_cols * sizeof(double);
+  double bytes = (nmax < 0) ? 0 : nmax*size_peratom_cols * sizeof(double);
   return bytes;
 }
 

src/USER-TALLY/compute_stress_tally.cpp

@@ -242,7 +242,7 @@ void ComputeStressTally::compute_peratom()
 
 double ComputeStressTally::memory_usage()
 {
-  double bytes = nmax*size_peratom_cols * sizeof(double);
+  double bytes = (nmax < 0) ? 0 : nmax*size_peratom_cols * sizeof(double);
   return bytes;
 }