Correct error message if no equations are available in the TableDialog.

src/main/java/de/neemann/digital/gui/components/table/TableDialog.java

@@ -595,13 +595,21 @@ public class TableDialog extends JDialog {
                 expressionListener = new ExpressionListenerJK(expressionListener);
 
             lastGeneratedExpressions = new ExpressionListenerStore(expressionListener);
-            new ExpressionCreator(model.getTable(), minimizer).create(lastGeneratedExpressions);
+            final int numVars = model.getTable().getVars().size();
+            new ExpressionCreator(model.getTable(), getMinimizer(numVars)).create(lastGeneratedExpressions);
 
         } catch (ExpressionException | FormatterException | AnalyseException e1) {
+            lastGeneratedExpressions = null;
             new ErrorMessage(Lang.get("msg_errorDuringCalculation")).addCause(e1).show();
         }
     }
 
+    private MinimizerInterface getMinimizer(int size) {
+        if (size<=4)
+            return new MinimizerQuineMcCluskeyExam();
+        else
+            return minimizer;
+    }
 
     private final class SizeAction extends AbstractAction {
         private int n;
@@ -680,6 +688,9 @@ public class TableDialog extends JDialog {
         }
 
         public void create(ExpressionListenerStore expressions) throws ExpressionException, FormatterException {
+            if (expressions==null)
+                throw new ExpressionException(Lang.get("err_noExpressionsAvailable"));
+
             ExpressionListener el = new ExpressionListener() {
                 @Override
                 public void resultFound(String name, Expression expression) throws FormatterException, ExpressionException {

src/main/resources/lang/lang_de.xml

@@ -449,6 +449,7 @@ Es sind nur {1} Variablen erlaubt, es wurden jedoch {2} gefunden.</string>
     <string name="err_processDoesNotTerminate_N">Der Prozess &quot;{0}&quot; wird nicht beendet!</string>
     <string name="err_processExitedWithError_N1_N2">Der Prozess meldet den Rückgabewert {0}: {1}</string>
     <string name="err_errorRunningFitter">Fehler beim Starten des externen Fitters!</string>
+    <string name="err_noExpressionsAvailable">Es liegen keine minimierten Gleichungen vor!</string>
 
     <string name="key_AddrBits">Adress-Bits</string>
     <string name="key_AddrBits_tt">Anzahl der Adress-Bits die verwendet werden.</string>

src/main/resources/lang/lang_en.xml

@@ -436,6 +436,7 @@ allowed are {1} variables but {2} are found.</string>
     <string name="err_processDoesNotTerminate_N">The process &quot;{0}&quot; does not return!</string>
     <string name="err_processExitedWithError_N1_N2">The process returns the non zero value {0}: {1}</string>
     <string name="err_errorRunningFitter">Error starting the external fitter!</string>
+    <string name="err_noExpressionsAvailable">There are no minimized equations!</string>
 
     <string name="key_AddrBits">Address Bits</string>
     <string name="key_AddrBits_tt">Number of address bits used.</string>