Fix bug in ProofManagementDialog (#3812)

Author: unp1

key.ui/src/main/java/de/uka/ilkd/key/gui/ProofManagementDialog.java

@@ -132,7 +132,10 @@ public Component getListCellRendererComponent(JList<?> list, Object value, int i
                     } else if (ps.getProofClosedByCache()) {
                         label.setIcon(KEY_CACHED_CLOSED);
                     } else {
-                        assert ps.getProofOpen();
+                        if (!ps.getProofOpen()) {
+                            LOGGER.warn("Unknown proof status " + ps
+                                + " in ProofManagementDialog. Displaying open icon.");
+                        }
                         label.setIcon(KEY_OPEN);
                     }
                 }
@@ -513,6 +516,8 @@ private void updateStartButton() {
                     startButton.setIcon(KEY_OPEN);
                 } else if (status.getProofClosedButLemmasLeft()) {
                     startButton.setIcon(KEY_ALMOST_CLOSED);
+                } else if (status.getProofClosedByCache()) {
+                    startButton.setIcon(KEY_CACHED_CLOSED);
                 } else {
                     assert status.getProofClosed();
                     startButton.setIcon(KEY_CLOSED);