Minimal ZDoom parser crash

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctype.h>

struct FParseSymbol
{
    int Value;
    char Sym[80];
};

union FParseToken
{
    int val;
    double fval;
    char sym[80];
    char string[80];
    FParseSymbol *symval;
};

static FParseSymbol symbols[10];
bool FindSym (char *sym, FParseSymbol **val)
{
    // Remove loop or if here to fix
    for(unsigned i=0;i<10; i++)
    {
        if (strcmp (symbols[i].Sym, sym) == 0)
        {
            *val = &symbols[i];
            return true;
        }
    }
    return false;
}

int GetToken (char *&sourcep, FParseToken *yylval)
{
    char token[80];
    int toksize;

    memset(token, 'a', 10);
    toksize = 10;
    token[toksize] = 0;

    // Remove this if line to fix
    if (FindSym (token, &yylval->symval)) return 0;
    strcpy (yylval->sym, token);

    // Replacing above strcpy with this works
    //memcpy(yylval->sym, token, 80);
    return 0;
}

int main()
{
    char* test = NULL;

    FParseToken sym;
    GetToken(test, &sym);
    return 0;
}