diff --git a/src/lib/iter-chain-search.hpp b/src/lib/iter-chain-search.hpp
index beeb69469..c662fb926 100644
--- a/src/lib/iter-chain-search.hpp
+++ b/src/lib/iter-chain-search.hpp
@@ -181,14 +181,17 @@ namespace iter {
       IterChainSearch&&                             >
       search (FUN&& configureSearchStep)
         {
-          Step nextStep{forward<FUN> (configureSearchStep)};
-          
-          if (_Base::isDisabled())
-            this-> filter() = move (nextStep (*this));     // immediately apply first step
-          else                                            //
-            stepChain_.emplace_back (move (nextStep));   //   append all further steps into the chain...
-                                                        //    then establish invariant:
-          this->iterNext();                            //     expand to leaf and forward to first match
+          if (not this->empty())
+            {
+              Step nextStep{forward<FUN> (configureSearchStep)};
+              
+              if (_Base::isDisabled())
+                this-> filter() = move (nextStep (*this));     // immediately apply first step
+              else                                            //
+                stepChain_.emplace_back (move (nextStep));   //   append all further steps into the chain...
+                                                            //    then establish invariant:
+              this->iterNext();                            //     expand to leaf and forward to first match
+            }
           return move(*this);
         }
       
diff --git a/src/lib/iter-tree-explorer.hpp b/src/lib/iter-tree-explorer.hpp
index 650e161f1..8e73566a4 100644
--- a/src/lib/iter-tree-explorer.hpp
+++ b/src/lib/iter-tree-explorer.hpp
@@ -187,6 +187,7 @@ namespace lib {
         COR &      _core()       { return static_cast<COR&>       (*this); }
         COR const& _core() const { return static_cast<COR const&> (*this); }
         
+      protected:
         void
         __throw_if_empty()  const
           {
@@ -754,6 +755,7 @@ namespace lib {
         void
         iterNext()
           {
+            SRC::__throw_if_empty();
             SRC::expandChildren();
           }
       };
@@ -786,6 +788,7 @@ namespace lib {
           {
             if (shallExpand_)
               {
+                SRC::__throw_if_empty();
                 SRC::expandChildren();
                 shallExpand_ = false;
               }
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index 886e792a8..7a982f05f 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -32106,8 +32106,6 @@
 <icon BUILTIN="button_ok"/>
 </node>
 </node>
-<node CREATED="1536539140421" ID="ID_1097764973" MODIFIED="1536539198310" TEXT="1.L&#xf6;sungsansatz">
-<icon BUILTIN="button_cancel"/>
 <node COLOR="#338800" CREATED="1536357917385" ID="ID_1615410357" MODIFIED="1536539160556" TEXT="wenn leer, dann direkt den Basis-Layer konfigurieren">
 <icon BUILTIN="button_ok"/>
 </node>
@@ -32120,17 +32118,22 @@
 <icon BUILTIN="flag-yellow"/>
 <node CREATED="1536539323716" ID="ID_1627599615" MODIFIED="1536539353260" TEXT="einmal beim direkten Rekonfigurieren"/>
 <node CREATED="1536539357408" ID="ID_834480997" MODIFIED="1536539373834" TEXT="dann nochmal generisch"/>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1536541001266" ID="ID_1480503625" MODIFIED="1536541008706" TEXT="in else-Zweig ziehen">
+<icon BUILTIN="flag-yellow"/>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1536539386764" ID="ID_487266350" MODIFIED="1536539429112" TEXT="ersch&#xf6;pfter Iter bricht ab">
-<arrowlink COLOR="#c5789c" DESTINATION="ID_1288939799" ENDARROW="Default" ENDINCLINATION="137;-5;" ID="Arrow_ID_1528021143" STARTARROW="None" STARTINCLINATION="-146;47;"/>
+</node>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1536539386764" ID="ID_487266350" MODIFIED="1536631289616" TEXT="ersch&#xf6;pfter Iter bricht ab">
+<arrowlink COLOR="#c5789c" DESTINATION="ID_1288939799" ENDARROW="Default" ENDINCLINATION="99;3;" ID="Arrow_ID_1528021143" STARTARROW="None" STARTINCLINATION="-35;27;"/>
 <icon BUILTIN="flag-yellow"/>
 </node>
 </node>
 </node>
+<node COLOR="#338800" CREATED="1536539286897" ID="ID_1288939799" MODIFIED="1536631289616" TEXT="overconstrained triggert Assertion">
+<linktarget COLOR="#c5789c" DESTINATION="ID_1288939799" ENDARROW="Default" ENDINCLINATION="99;3;" ID="Arrow_ID_1528021143" SOURCE="ID_487266350" STARTARROW="None" STARTINCLINATION="-35;27;"/>
+<icon BUILTIN="button_ok"/>
+<node CREATED="1536631251921" HGAP="51" ID="ID_588077559" MODIFIED="1536631280009" TEXT="sollte stattdessen leer werden" VSHIFT="23">
+<icon BUILTIN="yes"/>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1536539286897" ID="ID_1288939799" MODIFIED="1536539421685" TEXT="overconstrained triggert Assertion">
-<linktarget COLOR="#c5789c" DESTINATION="ID_1288939799" ENDARROW="Default" ENDINCLINATION="137;-5;" ID="Arrow_ID_1528021143" SOURCE="ID_487266350" STARTARROW="None" STARTINCLINATION="-146;47;"/>
-<icon BUILTIN="flag-yellow"/>
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1536357967826" ID="ID_634133289" MODIFIED="1536358245365" TEXT="clearFilter()">
 <icon BUILTIN="flag-yellow"/>