added testcase for categories with lincat C = {};

testsuite/check/lins/lins.gf

@@ -0,0 +1,9 @@
+abstract lins = {
+
+cat Nat ;
+cat C Nat ;
+
+fun zero : Nat ;
+    test : C zero ;
+
+}

testsuite/check/lins/lins.gfs

@@ -0,0 +1,2 @@
+i -erasing=on testsuite\check\lins\linsCnc.gf
+pg -printer=pmcfg_pretty

testsuite/check/lins/lins.gfs.gold

@@ -0,0 +1,12 @@
+language linsCnc␍
+productions␍
+  C1 -> F0[]␍
+functions␍
+  F0 := () [zero]␍
+sequences␍
+startcats␍
+  C := [C0]␍
+  Float := [Float]␍
+  Int := [Int]␍
+  Nat := [C1]␍
+  String := [String]␍

testsuite/check/lins/linsCnc.gf

@@ -0,0 +1,11 @@
+concrete linsCnc of lins = {
+
+lincat Nat =  {} ;
+
+-- we expect warnings because the lines bellow are commented out
+-- we don't expect warning for zero because Nat = {}
+
+-- lincat C = {s : Str} ;
+-- lin test = {s = "test"} ;
+
+}