[patch] use binary encoding function that does not overflow for qr

.gitignore

@@ -35,3 +35,4 @@ dist
 dev
 .nyc_output
 test-results.json
+.idea/

src/6_branch.js

@@ -1340,20 +1340,22 @@ Branch.prototype['qrCode'] = wrap(
 		this._api(
 			resources.qrCode,
 			utils.cleanLinkData(linkData),
-			function(error, rawBuffer) {
-				function QrCode() { }
-
-				if (!error) {
-					QrCode['rawBuffer'] = rawBuffer;
-					QrCode['base64'] = function() {
-						// First Encode array buffer as UTF-8 String, then Base64 Encode
-						if (this['rawBuffer']) {
-							return btoa(String.fromCharCode.apply(null, new Uint8Array(this['rawBuffer'])));
-						}
-						throw Error('QrCode.rawBuffer is empty.');
-					};
-				}
-				return done(error || null, QrCode || null);
+			(error, rawBuffer) => {
+				if (error) return done(error, null);
+
+				const QrCode = {
+					rawBuffer,
+					base64() {
+						if (!this.rawBuffer) throw new Error('QrCode.rawBuffer is empty.');
+						// Encode the Uint8Array to a binary string, then convert to base64
+						const binaryString = Array.from(new Uint8Array(this.rawBuffer))
+							.map(byte => String.fromCharCode(byte))
+							.join('');
+						return btoa(binaryString);
+					}
+				};
+
+				return done(null, QrCode);
 			}
 		);
 	}