avoid typescript error
avoid typescript error

keeps the following errors from happening when compiling:
```
node_modules/emailjs/smtp/mime.ts:109:15 - error TS2345: Argument of type 'string' is not assignable to parameter of type 'never'.

109             lines.push(curLine);
                           ~~~~~~~

node_modules/emailjs/smtp/mime.ts:206:3 - error TS2322: Type 'string[]' is not assignable to type 'never[]'.
  Type 'string' is not assignable to type 'never'.

206     parts =
        ~~~~~

node_modules/emailjs/smtp/mime.ts:220:16 - error TS2345: Argument of type 'string' is not assignable to parameter of type 'never'.

                                   ~~~~~~~~~~~~~~~~~~~~~~~

node_modules/emailjs/smtp/mime.ts:227:34 - error TS2345: Argument of type 'string' is not assignable to parameter of type 'never'.

227     str.substring(j) && parts.push(str.substring(j));
                                       ~~~~~~~~~~~~~~~~

node_modules/emailjs/smtp/mime.ts:228:3 - error TS2322: Type 'string[]' is not assignable to type 'never[]'.
  Type 'string' is not assignable to type 'never'.

228     parts = parts.map((x) => encoder.encode(x)).map((x) => encodeBase64(x));
        ~~~~~
```
eleith/emailjs,eleith/emailjs,eleith/emailjs