change julia wrapper of ivectorpair so that it doesn't lead to undefined...

change julia wrapper of ivectorpair so that it doesn't lead to undefined behavior in the case of wrong input data (cf. #629)

api/GenApi.py

@@ -186,8 +186,9 @@ def ivectorpair(name, value=None, python_value=None, julia_value=None):
     a.python_pre = api_name + ", " + api_name_n + " = _ivectorpair(" + name + ")"
     a.python_arg = api_name + ", " + api_name_n
     a.julia_ctype = "Ptr{Cint}, Csize_t"
-    a.julia_arg = ("convert(Vector{Cint}, collect(Cint, Iterators.flatten(" + name + "))), " +
-                   "2 * length(" + name + ")")
+    a.julia_pre = (api_name + " = collect(Cint, Iterators.flatten(" + name + "))\n    " +
+                   api_name_n + " = length(" + api_name + ")")
+    a.julia_arg = (api_name + ", " + api_name_n)
     return a
 
 def ivectorvectorint(name, value=None, python_value=None, julia_value=None):