default parameter values: fix crash

Fix crash when declaring default parameter values while current_procinfo
is not yet valid

resolves #40413

compiler/ninl.pas

@@ -492,9 +492,11 @@ implementation
           internalerror(2012032102);
 
         def:=ttypenode(left).typedef;
-        if df_generic in current_procinfo.procdef.defoptions then
+        if assigned(current_procinfo) and
+           (df_generic in current_procinfo.procdef.defoptions) then
           begin
-            { don't allow as a default parameter value }
+            { don't allow as a default parameter value, because it may not be valid
+              when specialising }
             if block_type<>bt_const then
               result:=cpointerconstnode.create(0,def)
             else

tests/webtbs/tw40413.pp

@@ -0,0 +1,67 @@
+{$mode objfpc}
+{$h+}
+{$codepage utf8}
+program defaulting;
+
+
+var
+  a: integer = 0;
+  b: integer = default(integer);
+
+function c (d: integer = 0): integer;
+  begin
+    result := d;
+  end;
+
+procedure g (h: integer = 0);
+  var
+    i: integer = default(integer);
+  begin
+    writeln(h, i);
+    if h<>0 then
+      halt(1);
+    if i<>0 then
+      halt(2);
+  end;
+
+procedure j (k: integer = default(integer));
+  var
+    l: integer = default(integer);
+  begin
+    writeln(k, l);
+    if k<>0 then
+      halt(3);
+    if l<>0 then
+      halt(4);
+  end;
+
+function e (f: integer = default(integer)): integer;
+  begin
+    result := f;
+  end;
+
+function m (n: string = default(string)): string;
+  var
+    o: string = '1';
+    p: string = default(string);
+    q: string = '';
+    r: string = '2';
+  begin
+    result := n + o + p + q + r;
+  end;
+
+begin
+  writeln(a, b, c);
+  if a<>0 then
+    halt(5);
+  if b<>0 then
+    halt(6);
+  if c<>0 then
+    halt(7);
+  g;
+  j;
+  writeln(m);
+  if m<>'12' then
+    halt(8);
+end.
+