update ReactionSystem constructors for defaults

Author: anandijain

src/networkapi.jl

@@ -283,7 +283,7 @@ Construct an empty [`ReactionSystem`](@ref). `iv` is the independent variable,
 usually time, and `name` is the name to give the `ReactionSystem`.
 """
 function make_empty_network(; iv=DEFAULT_IV, name=gensym(:ReactionSystem))
-    ReactionSystem(Reaction[], iv, [], [], Equation[], name, ReactionSystem[])
+    ReactionSystem(Reaction[], iv, [], [], Equation[], name, ReactionSystem[], Dict())
 end
 
 """

src/reaction_network.jl

@@ -125,7 +125,8 @@ macro reaction_network(name::Symbol=gensym(:ReactionSystem))
                                  [], 
                                  Equation[],
                                  $(QuoteNode(name)),
-                                 ReactionSystem[])))
+                                 ReactionSystem[],
+                                 Dict())))
 end
 
 ### Macros used for manipulating, and successively builing up, reaction systems. ###