Exception thrown;read access violation

[nolecelson]

Exception thrown: read access violation.
node was nullptr. line 55

-program is supposed to translate english to morse code vice versa but the program breaks at line 55 with the exception thrown and im having trouble solving it

#pragma comment(lib,"d3d9.lib")
#include <iostream>
#include <fstream>
#include <iomanip>
#include <ctime>
#include <string>
#include <cctype>
#include<stdlib.h>

using namespace std;
struct TREENODE {//constructor
	char letter;//to be replaced by a letter
	TREENODE* left;//declare pointer
	TREENODE* right;//declare pointer
	TREENODE() {
		letter = ' ';
		left = 0;
		right = 0;
	}
};
struct MORSECODE {//each morse code object has
	char letter;//english letters
	char code[100];//dots and dashed
};
class TELEGRAPH {//binary tree
private:
	static MORSECODE table[100];
	static TREENODE* root;
	static void destroyTree(TREENODE *NODE);
public:
	TELEGRAPH() {
		root = NULL;
	}
	static void buildTree();

	void Encode(char text[], char morse[]);
	void Decode(char morse[], char text[]);
};
MORSECODE TELEGRAPH::table[100] = {
   {'E', ". " }, { 'T', "- " }, { 'I', ".. " }, { 'A', ".- " }, { 'N', "-. " }, { 'M', "-- " },
   {'S', "... "}, {'U', "..- "}, {'R', ".-. "}, {'W', ".-- "}, {'D', "-.. "}, {'K', "-.- "},
   {'G', "--. "}, {'O', "--- "}, {'H', ".... "}, {'V', "...- "}, {'F', "..-. "}, {'L', ".-.. "},
   {'P', ".--. "}, {'J', ".--- "}, {'B', "-... "}, {'X', "-..- "},
   {'C', "-.-. "}, {'Y', "-.-- "}, {'Z', "--.. "}, {'Q', "--.- "}, {' ', "---- "}
};
TREENODE *TELEGRAPH::root = NULL;
void TELEGRAPH::Decode(char morse[], char text[]) {
	char* morsePtr;//points to the dots and dashes in the table
	TREENODE* node;//declare pointer
	node = root;
	cout << "Decode called" << endl;
	for (morsePtr = morse; *morsePtr; morsePtr++) {//goes through the morse code that letter/symbol
		if (*morsePtr != ' ') {
			if (*morsePtr == '.') {
				node = node->left;
			}
			else if (*morsePtr == '-') {
				node = node->right;
			}
		}
		else {
			node = root;
		}
		continue;
	}
	*text++ = node->letter;
	return;
}
void TELEGRAPH::Encode(char text[], char morse[]) {
	int i;
	char c, * t, * morsePtr;//goes through the morse code for that letter/symbol 
	cout << "encode called" << endl;
	cout << "\sending >>> ";
	for (t = text; *t; t++) {
		c = toupper(*t);
		if (c == ' ') {
			*morse++ =' ';
			continue;
		}
		for (i = 0; table[i].letter; i++) {
			if (table[i].letter == c)break;
		}
		if (!table[i].letter) {
			continue;
		}
		morsePtr = table[i].code;
		while (*morsePtr) {
			*morse++ = *morsePtr++;
		}
		*morse++ = ' ';
	}
};

void TELEGRAPH::buildTree() {
	TREENODE* node, * nextNode;
	char* morsePtr;
	root = new TREENODE;
	if (!root) {
		return;
	}
	root->letter = ' ';
	cout << "alphabet in morse";
	for (int i = 0; table[i].letter; i++) {
		node = root;
		for (morsePtr = table[i].code; *morsePtr; morsePtr++) {
			if (*morsePtr == ' ') {
				cout << *morsePtr;
				nextNode = new TREENODE;
				node->right = nextNode;
				node = node->right;
			}
			else if (*morsePtr == '.') {
				cout << *morsePtr;
				nextNode = new TREENODE;
				node->left = nextNode;
				node = node->left;
			}
		}
	}
};
int main() {
	TELEGRAPH station;
	char text[100], morse[600];
	station.buildTree();
	cout << "\enter sentence in english";
	cin.getline(text, 80);
	station.Encode(text, morse);
	cout << morse;
	cout << "message received";
	station.Decode(morse, text);
	cout << "message sent: " << text << endl;	
}

[Thomas1965]

The problem is on line 55 node = node->left;
node is just nullptr;

[dutch]

#include <iostream>
#include <sstream>
#include <algorithm>
#include <cstring>
using namespace std;

const char Morse[] {"**ETIANMSURWDKGOHVF*L*PJBXCYZQ* "};

char morse_to_char(const string& s) {
    int i = 1;
    for (char ch: s)
        if      (ch == '.') i = i * 2;
        else if (ch == '-') i = i * 2 + 1;
        else break;
    return i < int(sizeof Morse) - 1 ? Morse[i] : '*';
}

string morse_to_string(const string& m) {
    string r, token;
    istringstream in(m);
    while (in >> token) r += morse_to_char(token);
    return r;
}

string to_morse(char ch) {
    const char* p = strchr(Morse, toupper(ch));
    if (!p) return "*";
    string r;
    for (int i = p - Morse; i > 1; i /= 2) r += ".-"[i % 2];
    reverse(r.begin(), r.end());
    return r;
}

string to_morse(const string& s) {
    string r;
    for (char ch: s) { r += to_morse(ch); r += ' '; }
    return r;
}

int main() {
    string line;
    cout << "Enter some words: ";
    getline(cin, line);
    cout << to_morse(line) << '\n';

    cout << "Enter some morse code: ";
    getline(cin, line);
    cout << morse_to_string(line) << '\n';
}

[nolecelson]

thanks! but unfortunately we have to use a Binary search tree to translate it for an assignment:/