Bug 1258797 - Catch error when trying to open save as dialog to invalid path. r=Gijs

MozReview-Commit-ID: GbMgcfOgVaq

--HG--
extra : rebase_source : da89a0b7d2c66e8c744395f874a6b5fc61516454

toolkit/mozapps/downloads/DownloadLastDir.jsm

@@ -143,9 +143,13 @@ DownloadLastDir.prototype = {
         let file = plainPrefFile;
         if (aReason == Components.interfaces.nsIContentPrefCallback2.COMPLETE_OK &&
            result instanceof Components.interfaces.nsIContentPref) {
+          try {
             file = Components.classes["@mozilla.org/file/local;1"]
                              .createInstance(Components.interfaces.nsIFile);
             file.initWithPath(result.value);
+          } catch (e) {
+            file = plainPrefFile;
+          }
         }
         aCallback(file);
       }