[composer] Fix loss of alpha value for attribute table grid color whe…

…n project saved and restored

src/core/composer/qgscomposertable.cpp

@@ -248,6 +248,7 @@ bool QgsComposerTable::tableWriteXML( QDomElement& elem, QDomDocument & doc ) co
   elem.setAttribute( "gridColorRed", mGridColor.red() );
   elem.setAttribute( "gridColorGreen", mGridColor.green() );
   elem.setAttribute( "gridColorBlue", mGridColor.blue() );
+  elem.setAttribute( "gridColorAlpha", mGridColor.alpha() );
   elem.setAttribute( "showGrid", mShowGrid );
 
   //columns
@@ -282,7 +283,8 @@ bool QgsComposerTable::tableReadXML( const QDomElement& itemElem, const QDomDocu
   int gridRed = itemElem.attribute( "gridColorRed", "0" ).toInt();
   int gridGreen = itemElem.attribute( "gridColorGreen", "0" ).toInt();
   int gridBlue = itemElem.attribute( "gridColorBlue", "0" ).toInt();
-  mGridColor = QColor( gridRed, gridGreen, gridBlue );
+  int gridAlpha = itemElem.attribute( "gridColorAlpha", "255" ).toInt();
+  mGridColor = QColor( gridRed, gridGreen, gridBlue, gridAlpha );
 
   //restore column specifications
   qDeleteAll( mColumns );