small crashfixes

src/main/java/de/hhu/ba/yoshikoWrapper/core/Core.java

@@ -22,6 +22,7 @@ public class Core {
 		CyNetwork currentNetwork = cy.getCurrentNetwork();
 		if (currentNetwork == null) {
 			//TODO
+			return;
 		}
 		
 		LibraryInterface.setTimeLimit(timeLimit);

src/main/java/de/hhu/ba/yoshikoWrapper/gui/TimeLimitSetter.java

 package de.hhu.ba.yoshikoWrapper.gui;
 
+import java.awt.Dimension;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 
@@ -17,10 +18,9 @@ public class TimeLimitSetter extends JPanel{
 	private NumberInputField numberField;
 	
 	public TimeLimitSetter() {
-		checkBox = new JCheckBox();
+		checkBox = new JCheckBox("Use time limit (s):");
 		numberField = new NumberInputField();
 		numberField.setEnabled(false); //By default time limit is turned off
-		numberField.setSize(40, 10);
 		checkBox.addActionListener(
 				new ActionListener() {
 
@@ -37,7 +37,7 @@ public class TimeLimitSetter extends JPanel{
 	}
 	
 	public int getTimeLimit() {
-		if (checkBox.isSelected()) {
+		if (!checkBox.isSelected()) {
 			return -1;
 		}
 		return numberField.getTimeLimit();