Actually wait to finish writing the file before resolving the promise

awaiting `writeFileWithPromise` does not actually await writing the data
to a file. Fucking stupid bug, who hired me to work on this

src/main/encryptionAndDecryptionLib.ts

@@ -130,8 +130,13 @@ function writeFileWithPromise(path: string, data: Buffer): Promise<string> {
   return new Promise((resolve, reject) => {
     const stream = fs.createWriteStream(path, { flags: 'w+' });
     stream.on('error', reject);
-    stream.write(data);
+    stream.write(data, (err) => {
+      if (err) {
+        reject('Failed to write');
+      } else {
     resolve(path);
+      }
+    });
   });
 }