fixed memory leak

samples/strcat.noja

@@ -19,4 +19,4 @@ fun append_esclamation_mark(A, n)
 	return A;
 }
 
-print(append_esclamation_mark(D, 7), '\n');
+print(append_esclamation_mark(D, 3), '\n');

src/runtime/o_closure.c

@@ -1,3 +1,6 @@
+// NOTE: This data structure doesn't strictly depend on
+//       the runtime, so it could be moved to src/objects.
+
 #include "../utils/defs.h"
 #include "../objects/objects.h"
 

src/runtime/o_nfunc.c

@@ -73,7 +73,10 @@ static Object *call(Object *self, Object **argv, unsigned int argc, Heap *heap,
 					argv2[i] = Object_NewNone(heap, error);
 
 					if(argv2[i] == NULL)
-						return 0;
+						{
+							free(argv2);
+							return NULL;
+						}
 				}
 		}
 	else UNREACHABLE;