mojo: Fix findbugs issue on java generated code.

mojo/public/tools/bindings/generators/java_templates/struct_definition.tmpl

 {% from "constant_definition.tmpl" import constant_def %}
 {% from "enum_definition.tmpl" import enum_def %}
 
-{% macro encode(variable, kind, offset, bit, level=0) %}
+{% macro encode(variable, kind, offset, bit, level=0, check_for_null=True) %}
 {% if kind|is_pointer_array_kind %}
 {% set sub_kind = kind.kind %}
+{%   if check_for_null %}
 if ({{variable}} == null) {
     encoder{{level}}.encodeNullPointer({{offset}}, {{kind|is_nullable_kind|java_true_false}});
 } else {
+{%   else %}
+{
+{%   endif %}
     org.chromium.mojo.bindings.Encoder encoder{{level + 1}} = encoder{{level}}.encodePointerArray({{variable}}.length, {{offset}}, {{kind|array_expected_length}});
     for (int i{{level}} = 0; i{{level}} < {{variable}}.length; ++i{{level}}) {
         {{encode(variable~'[i'~level~']', sub_kind, 'DataHeader.HEADER_SIZE + org.chromium.mojo.bindings.BindingsHelper.POINTER_SIZE * i'~level, 0, level+1)|indent(8)}}
     }
 }
 {% elif kind|is_map_kind %}
 if ({{variable}} == null) {
     encoder{{level}}.encodeNullPointer({{offset}}, {{kind|is_nullable_kind|java_true_false}});
 } else {
     org.chromium.mojo.bindings.Encoder encoder{{level + 1}} = encoder{{level}}.encoderForMap({{offset}});
     int size{{level}} = {{variable}}.size();
     {{kind.key_kind|java_type}}[] keys{{level}} = {{kind.key_kind|array|new_array('size'~level)}};
     {{kind.value_kind|java_type}}[] values{{level}} = {{kind.value_kind|array|new_array('size'~level)}};
     int index{{level}} = 0;
     for (java.util.Map.Entry<{{kind.key_kind|java_type(true)}}, {{kind.value_kind|java_type(true)}}> entry{{level}} : {{variable}}.entrySet()) {
         keys{{level}}[index{{level}}] = entry{{level}}.getKey();
         values{{level}}[index{{level}}] = entry{{level}}.getValue();
     }
-    {{encode('keys'~level, kind.key_kind|array, 'DataHeader.HEADER_SIZE', 0, level+1)|indent(4)}}
-    {{encode('values'~level, kind.value_kind|array, 'DataHeader.HEADER_SIZE + org.chromium.mojo.bindings.BindingsHelper.POINTER_SIZE', 0, level+1)|indent(4)}}
+    {{encode('keys'~level, kind.key_kind|array, 'DataHeader.HEADER_SIZE', 0, level+1, False)|indent(4)}}
+    {{encode('values'~level, kind.value_kind|array, 'DataHeader.HEADER_SIZE + org.chromium.mojo.bindings.BindingsHelper.POINTER_SIZE', 0, level+1, False)|indent(4)}}
 }
 {% else %}
 encoder{{level}}.{{kind|encode_method(variable, offset, bit)}};
 {% endif %}
 {% endmacro %}
 
 {% macro decode(variable, kind, offset, bit, level=0) %}
 {% if kind|is_struct_kind or kind|is_pointer_array_kind or kind|is_map_kind %}
 org.chromium.mojo.bindings.Decoder decoder{{level+1}} = decoder{{level}}.readPointer({{offset}}, {{kind|is_nullable_kind|java_true_false}});
 {%   if kind|is_struct_kind %}
 {{variable}} = {{kind|java_type}}.decode(decoder{{level+1}});
 {%   else %}{# kind|is_pointer_array_kind or is_map_kind #}
+{%     if kind|is_nullable_kind %}
 if (decoder{{level+1}} == null) {
     {{variable}} = null;
 } else {
+{%     else %}
+{
+{%     endif %}
 {%     if kind|is_map_kind %}
     decoder{{level+1}}.readDataHeaderForMap();
     {{kind.key_kind|java_type}}[] keys{{level}};
     {{kind.value_kind|java_type}}[] values{{level}};
     {
         {{decode('keys'~level, kind.key_kind|array, 'DataHeader.HEADER_SIZE', 0, level+1)|indent(8)}}
     }
     {
         {{decode('values'~level, kind.value_kind|array('keys'~level~'.length'), 'DataHeader.HEADER_SIZE + org.chromium.mojo.bindings.BindingsHelper.POINTER_SIZE', 0, level+1)|indent(8)}}
     }
@@ skipping 78 matching lines @@
         org.chromium.mojo.bindings.Encoder encoder0 = encoder.getEncoderAtDataOffset(DEFAULT_STRUCT_INFO);
 {% endif %}
 {% for byte in struct.bytes %}
 {%   for packed_field in byte.packed_fields %}
         {{encode(packed_field.field|name, packed_field.field.kind, 8+packed_field.offset, packed_field.bit)|indent(8)}}
 {%   endfor %}
 {% endfor %}
     }
 }
 {% endmacro %}