Forward declaration results in SIGSEGV?

[readysloth]

Hello folks.

I was playing with nim around for a couple of weeks, but and now i struggle 
with forward declaration and later use of the function pointer.

Here is minimal example: 
    
    
    proc get_descriptions():string;
    
    type
        Function = object
            description: string
            action: (proc(): string)
    
    proc new_function(desc: string, act: proc():string = nil): Function=
        result.description = desc
        if act == nil:
            result.action = () => desc
    
    let functions={
        "help"    : new_function(desc = "help function",  act = 
get_descriptions),
        "start"   : new_function(desc = "start function" )
    }.toTable
    
    proc get_descriptions(): string =
        result = ""
        for k in functions.keys:
            result = fmt"{result} {k}: " & functions[k].description & "\n"
    
    echo functions["start"].action() # <-- executes normally
    echo functions["help"].action() # <-- issues "SIGSEGV: Illegal storage 
access. (Attempt to read from nil?)"
    
    
    Run

What am i doing wrong? Is it desired behaviour? If it is, how can i get around?

Thanks in advance!