fix invalid panel dx/dy offsets

[carandraug]

After parsing the JSON string, check if it's valid and fix it where we can. Fixes issue #292

[will-moore]

I've not tested yet but looks good.
We will be releasing figure 4.0.0 very soon so this won't go into that release I'm afraid.
I just noticed travis failed:

./omero_figure/scripts/omero/figure_scripts/Figure_To_Pdf.py:651:9: E266 too many leading '#' for block comment
./omero_figure/scripts/omero/figure_scripts/Figure_To_Pdf.py:652:9: E266 too many leading '#' for block comment

[carandraug]

I've not tested yet but looks good.
We will be releasing figure 4.0.0 very soon so this won't go into that release I'm afraid.

No problem. We already are using a modified version of the script that skips the annotation after the build.

I just noticed travis failed:

I have changed the comment style to follow pep 8

[sbesson]

This PR tries to address the bug described in #292 which had already been raised in #189 and tentatively fixed in #257 .

The proposed changes should handle the scenario where the dx key or the dy key exists but has a null value and set its value to DEFAULT_OFFSET in the context of the export script.

The change reverts the usage of dict.key(key, default) introduced in 77fd869. This logic would still be necessary if the keys could be missing under certain conditions as the script would raise a KeyError. Since the original PR (#257) was attempting to fix the same bug as here, it is possible the code path defining a default dictionary value in the getter was never used in practice. Leaving @will-moore to comment on this point.

Overall, 👍 for getting this into a 4.0.1.