Fix #97 undefined.startsWith read

Author: alexheretic

lib/competition.js

@@ -43,7 +43,10 @@ function showConflictingPackageWarnings() {
           text: "Disable ide-rust",
           onDidClick: () => {
             atom.notifications.getNotifications()
-              .filter(note => note.getOptions()._src.startsWith("ide-rust"))
+              .filter(note => {
+                const src = note.getOptions()._src
+                return src && src.startsWith("ide-rust")
+              })
               .forEach(note => note.dismiss())
             atom.packages.disablePackage("ide-rust")
           }