Fix parsing IDL oneway operations (#147)

Signed-off-by: Ricardo González Moreno <ricardo@richiware.dev>

src/main/antlr/com/eprosima/idl/parser/grammar/IDL.g4

@@ -2320,7 +2320,8 @@ op_decl [Vector<Annotation> annotations] returns [Pair<Operation, TemplateGroup>
         Vector<Pair<String, Token>> exceptions = null;
 }
     :   ( op_attribute { tkoneway=$op_attribute.token; } )?
-        op_type_spec { retType=$op_type_spec.returnPair.first(); template=$op_type_spec.returnPair.second();}
+        op_type_spec { if(null != $op_type_spec.returnPair) {retType=$op_type_spec.returnPair.first();
+            template=$op_type_spec.returnPair.second();}}
         {
             tk = _input.LT(1);
             name += tk.getText();

src/main/java/com/eprosima/idl/context/Context.java

@@ -113,12 +113,6 @@ public Context(
             m_file = m_file.substring(m_directoryFile.length());
          */
 
-        m_definitions = new ArrayList<Definition>();
-        m_modules = new HashMap<String, com.eprosima.idl.parser.tree.Module>();
-        m_interfaces = new HashMap<String, Interface>();
-        m_exceptions = new HashMap<String, com.eprosima.idl.parser.tree.Exception>();
-        m_types = new HashMap<String, TypeDeclaration>();
-        m_annotations = new HashMap<String, AnnotationDeclaration>();
         m_keywords = new HashSet<String>();
         fillKeywords();
 
@@ -795,6 +789,11 @@ public BitfieldSpec createBitfieldSpec(
         return object;
     }
 
+    public Collection<com.eprosima.idl.parser.tree.Exception> getExceptions()
+    {
+        return m_exceptions.values();
+    }
+
     public Collection<TypeDeclaration> getTypes()
     {
         return m_types.values();
@@ -1538,17 +1537,17 @@ public boolean is_enabled_custom_property_in_current_group(String custom_propert
     final String includeFlag = "-I";
 
     //! Store all global definitions.
-    private ArrayList<Definition> m_definitions;
+    private ArrayList<Definition> m_definitions = new ArrayList<Definition>();
     //! Map that contains all modules that were found processing the IDL file (after preprocessing):
-    private HashMap<String, com.eprosima.idl.parser.tree.Module> m_modules = null;
+    private HashMap<String, com.eprosima.idl.parser.tree.Module> m_modules = new HashMap<String, com.eprosima.idl.parser.tree.Module>();
     //! Map that contains all interfaces that were found processing the IDL file (after preprocessing):
-    private HashMap<String, Interface> m_interfaces = null;
+    private HashMap<String, Interface> m_interfaces = new HashMap<String, Interface>();
     //! Map that contains all global exceptions that were found processing the IDL file (after preprocessing).
-    private HashMap<String, com.eprosima.idl.parser.tree.Exception> m_exceptions = null;
+    private HashMap<String, com.eprosima.idl.parser.tree.Exception> m_exceptions = new HashMap<String, com.eprosima.idl.parser.tree.Exception>();
     //! Map that contains all types that were found processing the IDL file (after preprocessing).
-    protected HashMap<String, TypeDeclaration> m_types = null;
+    private HashMap<String, TypeDeclaration> m_types = new HashMap<String, TypeDeclaration>();
     //! Map that contains all annotations that where found processing the IDL file.
-    private HashMap<String, AnnotationDeclaration> m_annotations = null;
+    private HashMap<String, AnnotationDeclaration> m_annotations = new HashMap<String, AnnotationDeclaration>();
 
     private ArrayList<String> m_includePaths = null;
     //! Set that contains the library dependencies that were found because there was a line of the preprocessor.