Add constructors

app/src/main/java/com/keepassdroid/database/PwEntryV3.java

@@ -89,7 +89,6 @@ public class PwEntryV3 extends PwEntry {
 	private String           binaryDesc;
 	private byte[]          binaryData;
 
-
 	public PwEntryV3() {
 		super();
 	}

app/src/main/java/com/keepassdroid/database/PwEntryV4.java

@@ -61,6 +61,7 @@ public class PwEntryV4 extends PwEntry implements ITimeLogger {
 	private String tags = "";
 
 	public PwEntryV4() {
+	    super();
 	}
 	
 	public PwEntryV4(PwGroupV4 p) {

app/src/main/java/com/keepassdroid/database/PwGroupV3.java

@@ -37,6 +37,10 @@ public class PwGroupV3 extends PwGroup {
 	/** Used by KeePass internally, don't use */
 	private int flags;
 
+    public PwGroupV3() {
+        super();
+    }
+
 	@Override
 	public PwGroup getParent() {
 		return parent;

app/src/main/java/com/keepassdroid/database/PwGroupV4.java

@@ -43,7 +43,9 @@ public class PwGroupV4 extends PwGroup implements ITimeLogger {
 	private Boolean enableSearching = null;
 	private UUID lastTopVisibleEntry = PwDatabase.UUID_ZERO;
 
-	public PwGroupV4() {}
+	public PwGroupV4() {
+	    super();
+    }
 	
 	public PwGroupV4(String name, PwIconStandard icon) {
 		super.construct();