Fix PHP fatal error when doing 'undo' on a revision which exists but has no predecessors.

Failure of sanity checks for undo now shows warning instead of silent ignore.

diff --git a/includes/EditPage.php b/includes/EditPage.php
index f10d1ea..1c16dc2 100644 (file)
--- a/includes/EditPage.php
+++ b/includes/EditPage.php
@@ -102,11 +102,14 @@ class EditPage {
                                #Undoing a specific edit overrides section editing; section-editing
                                # doesn't work with undoing.
                                $undorev = Revision::newFromId($undo);
+                               $oldrev = $undorev ? $undorev->getPrevious() : null;
 
                                #Sanity check, make sure it's the right page.
                                # Otherwise, $text will be left as-is.
-                               if (!is_null($undorev) && $undorev->getPage() == $this->mArticle->getID()) {
-                                       $oldrev = $undorev->getPrevious();
+                               if( !is_null($undorev)
+                                       && !is_null( $oldrev )
+                                       && $undorev->getPage() == $this->mArticle->getID() ) {
+                                       
                                        $undorev_text = $undorev->getText();
                                        $oldrev_text = $oldrev->getText();
                                        $currev_text = $text;
@@ -118,17 +121,21 @@ class EditPage {
                                                $text = $oldrev_text;
                                                $result = true;
                                        }
+                               } else {
+                                       // Failed basic sanity checks.
+                                       // Older revisions may have been removed since the link
+                                       // was created, or we may simply have got bogus input.
+                                       $result = false;
+                               }
 
-                                       if( $result ) {
-                                               # Inform the user of our success and set an automatic edit summary
-                                               $this->editFormPageTop .= $wgOut->parse( wfMsgNoTrans( 'undo-success' ) );
-                                               $this->summary = wfMsgForContent( 'undo-summary', $undo, $undorev->getUserText() );
-                                               $this->formtype = 'diff';
-                                       } else {
-                                               # Warn the user that something went wrong
-                                               $this->editFormPageTop .= $wgOut->parse( wfMsgNoTrans( 'undo-failure' ) );
-                                       }
-
+                               if( $result ) {
+                                       # Inform the user of our success and set an automatic edit summary
+                                       $this->editFormPageTop .= $wgOut->parse( wfMsgNoTrans( 'undo-success' ) );
+                                       $this->summary = wfMsgForContent( 'undo-summary', $undo, $undorev->getUserText() );
+                                       $this->formtype = 'diff';
+                               } else {
+                                       # Warn the user that something went wrong
+                                       $this->editFormPageTop .= $wgOut->parse( wfMsgNoTrans( 'undo-failure' ) );
                                }
                        }
                        else if( $section != '' ) {