Fix problem with drawing of math backround with selections.

(cherry picked from commit 3e681bea4f)

src/mathed/InsetMathHull.cpp

@@ -510,7 +510,7 @@ void InsetMathHull::drawBackground(PainterInfo & pi, int x, int y) const
 		return;
 	} 
 	pi.pain.fillRectangle(x + 1, y - dim.asc + 1, dim.wid - 2,
-			dim.asc + dim.des - 1, backgroundColor(pi));
+			dim.asc + dim.des - 1, pi.backgroundColor(this));
 }
 
 

status.21x

@@ -113,6 +113,8 @@ What's new
 - Open View > Source Pane at a reasonable size (bug 9084). The downside of
   this fix is that the Source Pane cannot be shrunken ad infinitum anymore.
 
+- Fix problem with drawing of background in math when selection is active.
+
 
 * INTERNALS