patch 8.2.4556: test fails without the +job or +channel feature

Problem:    Test fails without the +job or +channel feature. (Dominique Pellé)
Solution:   Adjust #ifdefs.  Pass on skip flag. (closes #9942)
diff --git a/src/eval.c b/src/eval.c
index 1d57c38..3ecbf65 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3515,15 +3515,18 @@
 		    return OK;
 		}
 		break;
-#ifdef FEAT_JOB_CHANNEL
 	case 8: if (STRNCMP(s, "null_job", 8) == 0)
 		{
+#ifdef FEAT_JOB_CHANNEL
 		    rettv->v_type = VAR_JOB;
 		    rettv->vval.v_job = NULL;
+#else
+		    rettv->v_type = VAR_SPECIAL;
+		    rettv->vval.v_number = VVAL_NULL;
+#endif
 		    return OK;
 		}
 		break;
-#endif
 	case 9:
 		if (STRNCMP(s, "null_", 5) != 0)
 		    break;
@@ -3554,14 +3557,17 @@
 		}
 		break;
 	case 12:
-#ifdef FEAT_JOB_CHANNEL
 		if (STRNCMP(s, "null_channel", 12) == 0)
 		{
+#ifdef FEAT_JOB_CHANNEL
 		    rettv->v_type = VAR_CHANNEL;
 		    rettv->vval.v_channel = NULL;
+#else
+		    rettv->v_type = VAR_SPECIAL;
+		    rettv->vval.v_number = VVAL_NULL;
+#endif
 		    return OK;
 		}
-#endif
 		if (STRNCMP(s, "null_partial", 12) == 0)
 		{
 		    rettv->v_type = VAR_PARTIAL;
diff --git a/src/version.c b/src/version.c
index 20b5a03..ac3be8b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4556,
+/**/
     4555,
 /**/
     4554,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 25376d0..696301f 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -762,6 +762,7 @@
 {
     eap->getline = exarg_getline;
     eap->cookie = cctx;
+    eap->skip = cctx->ctx_skip == SKIP_YES;
 }
 
 /*
@@ -855,7 +856,8 @@
 	semsg(_(e_namespace_not_supported_str), name_start);
 	return NULL;
     }
-    if (check_defined(name_start, name_end - name_start, cctx,
+    if (cctx->ctx_skip != SKIP_YES
+	    && check_defined(name_start, name_end - name_start, cctx,
 							  NULL, FALSE) == FAIL)
 	return NULL;
     if (!ASCII_ISUPPER(is_global ? name_start[2] : name_start[0]))