First approach to solve MO20 compilation errors

Author: caev03

src/uniandes/tsdl/mutapk/operators/data/general/NullBackEndServiceReturn.java

@@ -7,6 +7,7 @@
 import org.antlr.runtime.tree.CommonTree;
 
 import uniandes.tsdl.antlr.smaliParser;
+import uniandes.tsdl.mutapk.helper.ASTHelper;
 import uniandes.tsdl.mutapk.helper.FileHelper;
 import uniandes.tsdl.mutapk.helper.Helper;
 import uniandes.tsdl.mutapk.helper.HexadecimalGenerator;
@@ -60,9 +61,10 @@ private void performMutationVariable(CommonTree tree, MutationLocation location,
 	private void performMutationParam(CommonTree tree, MutationLocation location, List<String> newLines, List<String> lines) {
 		// TODO Auto-generated method stub
 
-		CommonTree brother = (CommonTree) tree.getParent().getChild(tree.getChildIndex()+1);
+		CommonTree brother = ASTHelper.getFirstBrotherNamedOfType(smaliParser.I_STATEMENT_FORMAT11x, "move-result-object", tree);
 		String varName = brother.getChild(1).toString();
 
+		
 		for(int i=0; i < brother.getLine(); i++){
 			newLines.add(lines.get(i));
 		}

test/operators.properties

@@ -2,4 +2,7 @@
 # 15	=	BluetoothAdapterAlwaysEnabled
 # 31	=	InvalidIDFindView
 # 2	=	DifferentActivityIntentDefinition
-4	=	InvalidKeyIntentPutExtra
+#4	=	InvalidKeyIntentPutExtra
+#17	=	InvalidURI
+#28	=	InvalidColor
+20	=	NullBackEndServiceReturn