prevent illegal instruction exception when no measurements have been conducted

qdp_project/src/Benchmark.cpp

@@ -133,9 +133,11 @@ void process_timings(
             }
         }
 
+        if (scana_rc != 0) {
             *scana_run /= scana_rc;
             *scana_wait /= scana_rc;
         }
+    }
     {
         uint64_t scanb_rc = 0;
 
@@ -147,9 +149,11 @@ void process_timings(
             }
         }
 
+        if (scanb_rc != 0) {
             *scana_run /= scanb_rc;
             *scana_wait /= scanb_rc;
         }
+    }
     {
         uint64_t aggrj_rc = 0;
 
@@ -161,9 +165,11 @@ void process_timings(
             }
         }
 
+        if (aggrj_rc != 0) {
             *aggrj_run /= aggrj_rc;
             *aggrj_wait /= aggrj_rc;
         }
+    }
 }
 
 void scan_b(size_t gid, size_t tid) {