esa#299

Introduction of error handling mechanisms in the ACN encoding and decoding logic, specifically for external fields and octet strings containing external field functions.
Additionally, there's a minor update in the `CheckAsn1.fs` file related to the handling of the `MarkPresent` case for choice types.

FrontEndAst/CheckAsn1.fs

@@ -485,7 +485,7 @@ let rec isConstraintValid (t:Asn1Type) (c:Asn1Constraint) ast =
                     | Some(Optional opt), MarkAbsent,false  when opt.defaultValue.IsSome-> raise(SemanticError (loc, sprintf "Component %s has default value and therefore it cannot be constraint to ABSENT" conName))
                     | None, MarkAbsent,false
                     | None, MarkPresent,false             -> raise(SemanticError (loc, sprintf "Component %s is not optional. So, it cannot be constraint to ABSENT or PRESENT" conName))
-                    | _, MarkPresent, true
+                    | _, MarkPresent, true                -> ()
                     | _, MarkOptional, true               -> raise(SemanticError (loc, sprintf "Choice alternative %s cannot be constraint to PRESENT or OPTIONAL" conName))
                     | _                                   -> ()
             namedCons |> Seq.iter checkNamedConstraint

StgC/acn_c.stg

@@ -570,6 +570,7 @@ ret = (<if(noSizeMin)>(<noSizeMin>\<=<sExtFld>) && <endif>(<sExtFld>\<=<nSizeMax
 if (ret) {
     <p><sAcc>nCount = (int)<sExtFld>;
     ret = BitStream_DecodeOctetString_no_length(pBitStrm, <p><sAcc>arr, <p><sAcc>nCount);
+	<A(sErrCode)>
 }
 >>
 
@@ -582,6 +583,7 @@ oct_external_field_fix_size_decode(sTypedefName, p, sAcc, noSizeMin, nSizeMax, s
 ret = (<if(noSizeMin)>(<noSizeMin>\<=<sExtFld>) && <endif>(<sExtFld>\<=<nSizeMax>));
 if (ret) {
     ret = BitStream_DecodeOctetString_no_length(pBitStrm, <p><sAcc>arr, <nSizeMax>);
+	<A(sErrCode)>
 }
 >>
 
@@ -1129,6 +1131,7 @@ octet_string_containing_ext_field_func_decode(p, sFuncName, sReqBytesForUperEnco
 	*pErrCode = ret ? 0 : <sErrCode>;
 	if (ret) {
 		ret = BitStream_DecodeOctetString_no_length(pBitStrm, arr, (int)<sExtField>);
+		<A(sErrCode)>
 		if (ret) {
             pBitStrm = &bitStrm;
             <soInner>