Normalize zero dimension when generating regular array instance

[klayoutmatthias]

For test case and discussion see here: https://github.com/KLayout/klayout/issues/1096

The attached layout does not load properly when the library is not present.

[klayoutmatthias]

First analysis: the problem is likely cause by saving, not by reading. The test data linked above is already broken.

The PDK is taken from here: https://github.com/mabrains/sky130_klayout_pdk

Problem: while the layout loads properly with the library installed, it does not save properly. On GDS it gives broken hierarchy with additional top cells and on OASIS wrong layout.

[klayoutmatthias]

Changed title: the problem is cause by the Skywater device generator lib which creates arrays with a zero dimension of bmax (maybe amax too). This will screw up the DRC engine and stream writers. The script API should not allow generating such instances or normalize the dimensions to be at least 1.