[FIX] SAML login error.

[Hudell]

Closes #14664

[Stuw]

Aplied fix manually. It works.

--- /opt/rocketchat/programs/server/app/app.js.bak      2019-05-29 20:03:49.134198228 +0000
+++ /opt/rocketchat/programs/server/app/app.js  2019-05-29 20:21:34.620443576 +0000
@@ -109648,14 +109648,17 @@
     const fullName = loginResult.profile.cn || loginResult.profile.username || loginResult.profile.displayName;
     let eppnMatch = false; // Check eppn

-    let user = Meteor.users.findOne({
-      eppn: eduPersonPrincipalName
-    });
+    let user = null;

-    if (user) {
-      eppnMatch = true;
-    } // If eppn is not exist
+    if (eduPersonPrincipalName) {
+      user = Meteor.users.findOne({
+        eppn: eduPersonPrincipalName
+      });

+      if (user) {
+        eppnMatch = true;
+      } // If eppn is not exist
+    }

     if (!user) {
       user = Meteor.users.findOne({