Fixed attachment rule condition

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

@@ -214,7 +214,7 @@ public class EntityRule {
 
                 if (jcondition.has("mimetype")) {
                     String mimeType = jcondition.getString("mimetype");
-
+                    if (!TextUtils.isEmpty(mimeType)) {
                         boolean found = false;
                         for (EntityAttachment attachment : attachments)
                             if (mimeType.equalsIgnoreCase(attachment.getMimeType())) {
@@ -226,6 +226,7 @@ public class EntityRule {
                             return false;
                     }
                 }
+            }
 
             // Header
             JSONObject jheader = jcondition.optJSONObject("header");