fixed two findbugs issues

src/main/java/de/neemann/digital/core/NodeException.java

@@ -105,7 +105,7 @@ public class NodeException extends Exception {
                             }
 
                         }
-                    } catch (Exception e) {
+                    } catch (IllegalAccessException | NoSuchFieldException e) {
                         // ignore an error accessing the ElementTypeDescription
                     }
             }

src/main/java/de/neemann/digital/draw/library/NumStringComparator.java

@@ -70,6 +70,24 @@ public final class NumStringComparator implements Comparator<String> {
             }
         }
 
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (o == null || getClass() != o.getClass()) return false;
+
+            NumString numString = (NumString) o;
+
+            if (num != numString.num) return false;
+            return str != null ? str.equalsIgnoreCase(numString.str) : numString.str == null;
+        }
+
+        @Override
+        public int hashCode() {
+            int result = num;
+            result = 31 * result + (str != null ? str.toLowerCase().hashCode() : 0);
+            return result;
+        }
+
         @Override
         public int compareTo(NumString other) {
             if (isNum && other.isNum) {