ttcn3_sys_interface: Parse SIBs even when "StaticCellInfo" is missing

The test TC_9_2_1_1_1 sends a Cell->AddOrReconfigure->Basic message
without a "StaticCellInfo" member. This is used to change SIB1 of
the cell and simulate a different PLMN/TAC in the test.

handle_request_cell_basic() ignored the json message if "StaticCellInfo"
is missing which results in the SIB not being updated (PLMN stays as
00102 for example).
With this patch the SIBs after the json are now parsed even if there
"StaticCellInfo" is missing. A confirmation of the json is not sent
because the test does not seem to expect one in that case.

Related: TC_9_2_1_1_1

srsue/test/ttcn3/hdr/ttcn3_sys_interface.h

@@ -121,6 +121,10 @@ private:
 
   void handle_request_cell_basic(Document& document, const uint8_t* payload, const uint16_t len)
   {
+    // That is the cellId or name that the testsuites uses to refer to a specific cell
+    const Value& cell_name = document["Common"]["CellId"];
+    assert(cell_name.IsString());
+
     if (document["Request"]["Cell"]["AddOrReconfigure"]["Basic"].HasMember("StaticCellInfo")) {
       // Extract EARFCN
       const Value& earfcn =
@@ -155,13 +159,10 @@ private:
           document["Request"]["Cell"]["AddOrReconfigure"]["Basic"]["InitialCellPower"]["MaxReferencePower"];
       assert(ref_power.IsInt());
 
-      // That is the cellId or name that the testsuites uses to refer to a specific cell
-      const Value& cell_name = document["Common"]["CellId"];
-      assert(cell_name.IsString());
-
       // Now configure cell
       syssim->set_cell_config(
           ttcn3_helpers::get_timing_info(document), cell_name.GetString(), earfcn.GetInt(), cell, ref_power.GetInt());
+    }
 
     // Pull out SIBs and send to syssim
     uint16_t       consumed_bytes = 0;
@@ -182,6 +183,7 @@ private:
       consumed_bytes = payload_ptr - payload;
     }
 
+    if (document["Request"]["Cell"]["AddOrReconfigure"]["Basic"].HasMember("StaticCellInfo")) {
       // Create response for template car_CellConfig_CNF(CellId_Type p_CellId)
       std::string resp = ttcn3_helpers::get_basic_sys_req_cnf(cell_name.GetString(), "Cell");