Demo: Fixed incorrectly formed string passed to Combo (#298)

imgui_demo.cpp

@@ -1999,7 +1999,7 @@ static void ShowExampleAppLongText(bool* opened)
     static ImGuiTextBuffer log;
     static int lines = 0;
     ImGui::Text("Printing unusually long amount of text.");
-    ImGui::Combo("Test type", &test_type, "Single call to TextUnformatted()\0Multiple calls to Text(), clipped manually\0Multiple calls to Text(), not clipped"); 
+    ImGui::Combo("Test type", &test_type, "Single call to TextUnformatted()\0Multiple calls to Text(), clipped manually\0Multiple calls to Text(), not clipped\0"); 
     ImGui::Text("Buffer contents: %d lines, %d bytes", lines, log.size());
     if (ImGui::Button("Clear")) { log.clear(); lines = 0; }
     ImGui::SameLine();