Index: binaries/data/mods/public/gui/common/tab_buttons.js
===================================================================
--- binaries/data/mods/public/gui/common/tab_buttons.js
+++ binaries/data/mods/public/gui/common/tab_buttons.js
@@ -1,4 +1,9 @@
 /**
+ * Boolean indicating whether the tabs are initialized.
+ */
+var g_TabIsInit = false;
+
+/**
  * Number of categories.
  */
 var g_TabCategoryCount;
@@ -47,6 +52,7 @@
 
 		Engine.GetGUIObjectByName("tabButtonText[" + category + "]").caption = categoriesData[category].label;
 	}
+	g_TabIsInit = true;
 
 	selectPanel(g_TabCategorySelected);
 }
@@ -57,11 +63,12 @@
  */
 function selectNextTab(direction)
 {
-	selectPanel(g_TabCategorySelected === undefined ?
-		direction > 0 ?
-			0 :
-			g_TabCategoryCount - 1 :
-		(g_TabCategorySelected + direction + g_TabCategoryCount) % g_TabCategoryCount);
+	if (g_TabIsInit)
+		selectPanel(g_TabCategorySelected === undefined ?
+			direction > 0 ?
+				0 :
+				g_TabCategoryCount - 1 :
+			(g_TabCategorySelected + direction + g_TabCategoryCount) % g_TabCategoryCount);
 }
 
 function selectPanel(category)