Add a @NULLCHECK and an @assert for function name length

Author: quinnj

src/UDF.jl

@@ -1,5 +1,6 @@
 # scalar functions
 function registerfunc(db::SQLiteDB, nargs::Integer, func::Function, isdeterm::Bool=true; name="")
+    @assert sizeof(name) <= 255 "size of function name must be <= 255"
     @assert (-1 <= nargs <= 127) "nargs must follow the inequality -1 <= nargs <= 127"
 
     name = isempty(name) ? string(func) : name::String

src/api.jl

@@ -297,6 +297,7 @@ function sqlite3_create_function_v2(db::Ptr{Void},name::String,nargs::Integer,
                                     step::Ptr{Void},final::Ptr{Void},
                                     destructor::Ptr{Void})
     return ccall(
+        @NULLCHECK db
         (:sqlite3_create_function_v2, sqlite3_lib),
         Cint,
         (Ptr{Void}, Ptr{Uint8}, Cint, Cint, Ptr{Void},