fixes #2070

tests/gc/growobjcrash.nim

@@ -0,0 +1,29 @@
+discard """
+  output: "works"
+"""
+
+import cgi, strtabs
+
+proc handleRequest(query: string): StringTableRef =
+  iterator foo(): StringTableRef {.closure.} =
+    var params = {:}.newStringTable()
+    for key, val in cgi.decodeData(query):
+      params[key] = val
+    yield params
+
+  let x = foo
+  result = x()
+
+const Limit = when compileOption("gc", "markAndSweep"): 5*1024*1024 else: 500_000
+
+proc main =
+  var counter = 0
+  for i in 0 .. 100_000:
+    for k, v in handleRequest("nick=Elina2&type=activate"):
+      inc counter
+      if counter mod 100 == 0:
+        if getOccupiedMem() > Limit:
+          quit "but now a leak"
+
+main()
+echo "works"