fix crashes (info/toggle buttons, resize left panel) if no preview image has been loaded

rtgui/editorpanel.cc

@@ -505,6 +505,8 @@ void EditorPanel::error (Glib::ustring descr) {
 
 void EditorPanel::info_toggled () {
 
+    if(!ipc)
+        return;
     Glib::ustring infoString;
 
     const rtengine::ImageMetaData* idata = ipc->getInitialImage()->getMetaData();
@@ -912,6 +914,9 @@ void EditorPanel::historyBeforeLineChanged (const rtengine::procparams::ProcPara
 
 void EditorPanel::beforeAfterToggled () {
 
+    if(!ipc)
+        return;
+
     removeIfThere (beforeAfterBox,  beforeBox, false);
     removeIfThere (afterBox,  afterLabel, false);