check error code on basic_subs too

Author: isuruf

src/subs.jl

@@ -24,7 +24,8 @@ function subs(ex::T, var::S, val) where {T<:SymbolicType, S<:SymbolicType}
 end
 function subs(ex::T, d::CMapBasicBasic) where T<:SymbolicType
     s = Basic()
-    ccall((:basic_subs, libsymengine), Nothing, (Ref{Basic}, Ref{Basic}, Ptr{Cvoid}), s, ex, d.ptr)
+    err_code = ccall((:basic_subs, libsymengine), Cuint, (Ref{Basic}, Ref{Basic}, Ptr{Cvoid}), s, ex, d.ptr)
+    throw_if_error(err_code, ex)
     return s
 end