Fix "ascii" charset

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -800,13 +800,11 @@ public class MessageHelper {
                 ContentType ct = new ContentType(part.getContentType());
                 String charset = ct.getParameter("charset");
 
-                String encoding = null;
+                // Fix common mistakes
-                try {
+                if (charset != null) {
-                    String[] enc = part.getHeader("Content-Transfer-Encoding");
+                    charset = charset.replace("\"", "");
-                    if (enc != null && enc.length > 0)
+                    if ("ASCII".equals(charset.toUpperCase()))
-                        encoding = enc[0];
+                        charset = "us-ascii";
-                } catch (MessagingException ex) {
-                    Log.w(ex);
                 }
 
                 if (TextUtils.isEmpty(charset) || "US-ASCII".equals(charset.toUpperCase())) {