Adds sanity check on UINavigation to avoid crashes if there are no pages in the stack.

Removes button to fill import terrain images temporarily to contend with limitations in asset creation workflow
Adds sanity check to saving terrain material that obligates setting of diffuse and detail maps so everything displays and blends properly

Templates/BaseGame/game/data/UI/scripts/menuNavigation.tscript

@@ -75,7 +75,8 @@ function UINavigation::pushPage(%this, %newPage, %callback)
    }
    
    //don't re-add pages
-   if(%this.pageStack.getIndexFromKey(%newPage) != -1)
+   if(%this.pageStack.getPageCount() != 0 && 
+      %this.pageStack.getIndexFromKey(%newPage) != -1)
       return;
    
    %canChange = true;

Templates/BaseGame/game/tools/assetBrowser/scripts/assetTypes/terrain.tscript

@@ -5,9 +5,9 @@ function AssetBrowser::setupCreateNewTerrainAsset(%this)
    NewAssetPropertiesInspector.addField("genWithNoise", "Generate Terrain With Noise", "bool",  "Is this script used on the server?", "0", "2", %this.newAssetSettings);
    NewAssetPropertiesInspector.endGroup();
    
-   NewAssetPropertiesInspector.startGroup("Terrain - Import");
+   /*NewAssetPropertiesInspector.startGroup("Terrain - Import");
    NewAssetPropertiesInspector.addField("importDetails", "Import Heightmap", "button",  "Import an existing heightmap", "", "Canvas.pushDialog( TerrainImportGui );", %this.newAssetSettings);
-   NewAssetPropertiesInspector.endGroup();
+   NewAssetPropertiesInspector.endGroup();*/
 }
 
 function AssetBrowser::createTerrainAsset(%this)

Templates/BaseGame/game/tools/worldEditor/scripts/interfaces/terrainMaterialDlg.ed.tscript

@@ -153,6 +153,14 @@ function TerrainMaterialDlg::dialogApply( %this )
 {
    // Move all new materials we have created to the root group.
    
+   if(%this-->diffuseMapAssetId.text $= "None" ||
+   %this-->detailMapAssetId.text $= "None")
+   {
+      toolsMessageBoxOK("Invalid Terrain Material",
+                  "Terrain Materials require Diffuse and Detail textures to display and blend correctly.");
+      return;
+   }
+   
    %newCount = TerrainMaterialDlgNewGroup.getCount();
    for( %i = 0; %i < %newCount; %i ++ )
       RootGroup.add( TerrainMaterialDlgNewGroup.getObject( %i ) );