crash field model

from PyQt4 import QtCore, QtGui
from qgis.gui import QgsFieldExpressionWidget, QgsMapLayerComboBox, QgsMapLayerProxyModel

try:
    _fromUtf8 = QtCore.QString.fromUtf8
except AttributeError:
    def _fromUtf8(s):
        return s
try:
    _encoding = QtGui.QApplication.UnicodeUTF8
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig, _encoding)
except AttributeError:
    def _translate(context, text, disambig):
        return QtGui.QApplication.translate(context, text, disambig)

class Ui_ProjectSearch(object):
    def setupUi(self, ProjectSearch):
        ProjectSearch.setObjectName(_fromUtf8("ProjectSearch"))
        ProjectSearch.resize(324, 268)
        self.formLayout = QtGui.QFormLayout(ProjectSearch)
        self.formLayout.setObjectName(_fromUtf8("formLayout"))
        self.FieldNameLabel = QtGui.QLabel(ProjectSearch)
        self.FieldNameLabel.setObjectName(_fromUtf8("FieldNameLabel"))
        self.formLayout.setWidget(4, QtGui.QFormLayout.LabelRole, self.FieldNameLabel)
        self.label = QtGui.QLabel(ProjectSearch)
        self.label.setObjectName(_fromUtf8("label"))
        self.formLayout.setWidget(0, QtGui.QFormLayout.LabelRole, self.label)
        self.searchName = QtGui.QLineEdit(ProjectSearch)
        self.searchName.setObjectName(_fromUtf8("searchName"))
        self.formLayout.setWidget(0, QtGui.QFormLayout.FieldRole, self.searchName)
        self.layerLabel = QtGui.QLabel(ProjectSearch)
        sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.Minimum, QtGui.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.layerLabel.sizePolicy().hasHeightForWidth())
        self.layerLabel.setSizePolicy(sizePolicy)
        self.layerLabel.setObjectName(_fromUtf8("layerLabel"))
        self.formLayout.setWidget(1, QtGui.QFormLayout.LabelRole, self.layerLabel)
        self.layerCombo = QgsMapLayerComboBox(ProjectSearch)
        sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.MinimumExpanding, QtGui.QSizePolicy.Fixed)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.layerCombo.sizePolicy().hasHeightForWidth())
        self.layerCombo.setSizePolicy(sizePolicy)
        self.layerCombo.setSizeAdjustPolicy(QtGui.QComboBox.AdjustToContents)
        self.layerCombo.setObjectName(_fromUtf8("layerCombo"))
        self.formLayout.setWidget(1, QtGui.QFormLayout.FieldRole, self.layerCombo)
        self.label_2 = QtGui.QLabel(ProjectSearch)
        self.label_2.setObjectName(_fromUtf8("label_2"))
        self.formLayout.setWidget(6, QtGui.QFormLayout.LabelRole, self.label_2)
        self.priorityBox = QtGui.QSpinBox(ProjectSearch)
        self.priorityBox.setMinimum(1)
        self.priorityBox.setMaximum(999)
        self.priorityBox.setProperty("value", 1)
        self.priorityBox.setObjectName(_fromUtf8("priorityBox"))
        self.formLayout.setWidget(6, QtGui.QFormLayout.FieldRole, self.priorityBox)
        self.gridLayout = QtGui.QGridLayout()
        self.gridLayout.setObjectName(_fromUtf8("gridLayout"))
        self.label_3 = QtGui.QLabel(ProjectSearch)
        sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.MinimumExpanding, QtGui.QSizePolicy.MinimumExpanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label_3.sizePolicy().hasHeightForWidth())
        self.label_3.setSizePolicy(sizePolicy)
        self.label_3.setWordWrap(True)
        self.label_3.setObjectName(_fromUtf8("label_3"))
        self.gridLayout.addWidget(self.label_3, 0, 1, 1, 1)
        self.evaluateCheckBox = QtGui.QCheckBox(ProjectSearch)
        self.evaluateCheckBox.setText(_fromUtf8(""))
        self.evaluateCheckBox.setChecked(True)
        self.evaluateCheckBox.setObjectName(_fromUtf8("evaluateCheckBox"))
        self.gridLayout.addWidget(self.evaluateCheckBox, 0, 0, 1, 1)
        self.formLayout.setLayout(8, QtGui.QFormLayout.SpanningRole, self.gridLayout)
        self.buttonBox = QtGui.QDialogButtonBox(ProjectSearch)
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtGui.QDialogButtonBox.Cancel|QtGui.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName(_fromUtf8("buttonBox"))
        self.formLayout.setWidget(10, QtGui.QFormLayout.FieldRole, self.buttonBox)
        self.fieldExpressionWidget = QgsFieldExpressionWidget(ProjectSearch)
        self.fieldExpressionWidget.setObjectName(_fromUtf8("fieldExpressionWidget"))
        self.formLayout.setWidget(4, QtGui.QFormLayout.FieldRole, self.fieldExpressionWidget)

        self.retranslateUi(ProjectSearch)
        QtCore.QObject.connect(self.buttonBox, QtCore.SIGNAL(_fromUtf8("accepted()")), ProjectSearch.accept)
        QtCore.QObject.connect(self.buttonBox, QtCore.SIGNAL(_fromUtf8("rejected()")), ProjectSearch.reject)
        QtCore.QMetaObject.connectSlotsByName(ProjectSearch)

    def retranslateUi(self, ProjectSearch):
        ProjectSearch.setWindowTitle(_translate("ProjectSearch", "QuickFinder :: add local search layer", None))
        self.FieldNameLabel.setText(_translate("ProjectSearch", "Field", None))
        self.label.setText(_translate("ProjectSearch", "Search name", None))
        self.layerLabel.setText(_translate("ProjectSearch", "Layer", None))
        self.label_2.setText(_translate("ProjectSearch", "Priority", None))
        self.label_3.setText(_translate("ProjectSearch", "evaluate search directly (uncheck for multiple inserts)", None))

class ProjectSearchDialog(QtGui.QDialog, Ui_ProjectSearch):
    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.setupUi(self)

        self.layerCombo.setFilters(QgsMapLayerProxyModel.VectorLayer)
        self.layerCombo.layerChanged.connect(self.fieldExpressionWidget.setLayer)
        self.fieldExpressionWidget.setLayer(self.layerCombo.currentLayer())

        self.searchName.setText('test')

dlg = ProjectSearchDialog()
dlg.show()