patch 8.2.2842: Vim9: skip argument to searchpair() is not compiled

Problem:    Vim9: skip argument to searchpair() is not compiled.
Solution:   Add VAR_INSTR.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 5383d09..a0caf3d 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2989,6 +2989,7 @@
 	case VAR_UNKNOWN:
 	case VAR_ANY:
 	case VAR_VOID:
+	case VAR_INSTR:
 	    internal_error_no_abort("f_empty(UNKNOWN)");
 	    n = TRUE;
 	    break;
@@ -6303,6 +6304,7 @@
 	case VAR_PARTIAL:
 	case VAR_JOB:
 	case VAR_CHANNEL:
+	case VAR_INSTR:
 	    emsg(_("E701: Invalid type for len()"));
 	    break;
     }
@@ -10215,6 +10217,7 @@
 	case VAR_JOB:     n = VAR_TYPE_JOB; break;
 	case VAR_CHANNEL: n = VAR_TYPE_CHANNEL; break;
 	case VAR_BLOB:    n = VAR_TYPE_BLOB; break;
+	case VAR_INSTR:   n = VAR_TYPE_INSTR; break;
 	case VAR_UNKNOWN:
 	case VAR_ANY:
 	case VAR_VOID: