Updated ImGui.

3rdparty/ocornut-imgui/imgui.h

@@ -888,7 +888,8 @@ public:
         if (new_capacity <= Capacity) return;
         T* new_data = (value_type*)ImGui::MemAlloc((size_t)new_capacity * sizeof(value_type));
         memset(&new_data[Size], 0, (size_t)(new_capacity - Size) * sizeof(value_type)); // BK - clear garbage so that 0 initialized ImString works properly.
-        memcpy(new_data, Data, (size_t)Size * sizeof(value_type));
+        if (Data)
+            memcpy(new_data, Data, (size_t)Size * sizeof(value_type));
         ImGui::MemFree(Data);
         Data = new_data;
         Capacity = new_capacity;