patch 8.2.2578: Lua cannot handle a passed in lambda

Problem:    Lua cannot handle a passed in lambda.
Solution:   Handle VAR_PARTIAL. (Prabir Shrestha, closes #7937, closes #7936)
diff --git a/src/if_lua.c b/src/if_lua.c
index e202983..abcd850 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -568,6 +568,11 @@
 	case VAR_FUNC:
 	    luaV_pushfuncref(L, tv->vval.v_string);
 	    break;
+	case VAR_PARTIAL:
+	    // TODO: handle partial arguments
+	    luaV_pushfuncref(L, partial_name(tv->vval.v_partial));
+	    break;
+
 	case VAR_BLOB:
 	    luaV_pushblob(L, tv->vval.v_blob);
 	    break;