[.match-solution-grouped] body is incorrectly filled with the section dividers === / ==

Describe the bug [.match-solution-grouped] body is incorrectly filled with the section dividers

To Reproduce Parse the following bitmark to produce JSON output:

[.match-solution-grouped:bitmark--]
[@id:245334]
[%1][%HK E.1 Infektionslehre]
[!Ordnen Sie die deutschen Begriffe den Fachbegriffen zu.]
===
Überwärmung
==
Calor
===
Rötung
==
Rubor
===
Schmerzen
==
Dolor
===
eingeschränkte Funktion
==
Functio laesa
===
Schwellung
==
Tumor
===

The following JSON is produced:

 {
   "bitmark": "[.match-solution-grouped:bitmark--]\n[@id:245334]\n[%1][%HK E.1 Infektionslehre]\n[!Ordnen Sie die deutschen Begriffe den Fachbegriffen zu.]\n===\nÜberwärmung\n==\nCalor\n===\nRötung\n==\nRubor\n===\nSchmerzen\n==\nDolor\n===\neingeschränkte Funktion\n==\nFunctio laesa\n===\nSchwellung\n==\nTumor\n===",
   "bit": {
     "type": "match-solution-grouped",
     "format": "bitmark--",
     "item": "1",
     "heading": {},
     "pairs": [
       {
         "key": "Überwärmung",
         "values": [
           "Calor"
         ],
         "item": "",
         "hint": "",
         "instruction": "",
         "isCaseSensitive": true,
         "isExample": false,
         "example": "",
         "isLongAnswer": false
       },
       {
         "key": "Rötung",
         "values": [
           "Rubor"
         ],
         "item": "",
         "hint": "",
         "instruction": "",
         "isCaseSensitive": true,
         "isExample": false,
         "example": "",
         "isLongAnswer": false
       },
       {
         "key": "Schmerzen",
         "values": [
           "Dolor"
         ],
         "item": "",
         "hint": "",
         "instruction": "",
         "isCaseSensitive": true,
         "isExample": false,
         "example": "",
         "isLongAnswer": false
       },
       {
         "key": "eingeschränkte Funktion",
         "values": [
           "Functio laesa"
         ],
         "item": "",
         "hint": "",
         "instruction": "",
         "isCaseSensitive": true,
         "isExample": false,
         "example": "",
         "isLongAnswer": false
       },
       {
         "key": "Schwellung",
         "values": [
           "Tumor"
         ],
         "item": "",
         "hint": "",
         "instruction": "",
         "isCaseSensitive": true,
         "isExample": false,
         "example": "",
         "isLongAnswer": false
       }
     ],
     "body": "===\n\n==\n===\n\n==\n===\n\n==\n===\n\n==\n===\n\n==\n===",
     "id": [
       "245334"
     ],
     "lead": "HK E.1 Infektionslehre",
     "instruction": "Ordnen Sie die deutschen Begriffe den Fachbegriffen zu."
   }
 }

Expected behavior I think the body should be empty in this case, or populated with a body if there is one.

versions 1.0.38

bitmark-standard / bitmark-grammar

[.match-solution-grouped] body is incorrectly filled with the section dividers === / == #8