update some comments

src/problem/problem.cpp

@@ -460,7 +460,7 @@ VectorComposite Problem::getState(const StateStructure& _structure) const
         }
     }
 
-    // check for empty blocks and fill them with the last KF, or with zeros in the worst case
+    // check for empty blocks and fill them with the last KF, with the prior, or with zeros in the worst case
 
     VectorComposite state_last;
 
@@ -510,7 +510,7 @@ VectorComposite Problem::getState (const TimeStamp& _ts, const StateStructure& _
         }
     }
 
-    // check for empty blocks and fill them with the closest KF to ts, or with zeros in the worst case
+    // check for empty blocks and fill them with the closest KF to ts, with the prior, or with zeros in the worst case
 
     VectorComposite state_last;