[JUNGFRAU][CORRECT] Fix/store roi only if defined

Description

A bug was introduced here https://git.xfel.eu/detectors/pycalibration/-/merge_requests/762/diffs that lead to creating CONTROL and INSTRUMENT sections for ROI even if none was defined.

How Has This Been Tested?

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

Reviewers

@kluyvert

notebooks/Jungfrau/Jungfrau_Gain_Correct_and_Verify_NBC.ipynb

@@ -440,9 +440,10 @@
     "    module_no = int(karabo_da[-2:])\n",
     "    params_source = f'{karabo_id}/ROIPROC/{karabo_da}'\n",
     "    rois_source = f'{params_source}:output'\n",
-    "    # Create Instrument and Control sections to later add datasets.\n",
-    "    outp_source = ofile.create_instrument_source(rois_source)\n",
-    "    ctrl_source = ofile.create_control_source(params_source)\n",
+    "    if roi_definitions != [-1]:\n",
+    "        # Create Instrument and Control sections to later add datasets.\n",
+    "        outp_source = ofile.create_instrument_source(rois_source)\n",
+    "        ctrl_source = ofile.create_control_source(params_source)\n",
     "    for i in range(len(roi_definitions) // 6):\n",
     "        roi_module, a1, a2, b1, b2, mean_axis = roi_definitions[i*6 : (i+1)*6]\n",
     "        if roi_module == module_no:\n",