Fix crash in wxDC::GetMultiLineTextExtent() after last commit.

Don't call wxTextMeasure::DoGetTextExtent() with NULL width pointer, it now
supposes that both width and height pointers are non-NULL.

Add at least a trivial unit test for GetMultiLineTextExtent().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72700 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/graphics/measuring.cpp

@@ -95,6 +95,13 @@ void MeasuringTextTestCase::DCGetTextExtent()
     wxClientDC dc(wxTheApp->GetTopWindow());
 
     DoTestGetTextExtent(dc);
+
+    int w;
+    dc.GetMultiLineTextExtent("Good\nbye", &w, NULL);
+    const wxSize sz = dc.GetTextExtent("Good");
+    CPPUNIT_ASSERT_EQUAL( sz.x, w );
+
+    CPPUNIT_ASSERT( dc.GetMultiLineTextExtent("Good\nbye").y >= 2*sz.y );
 }
 
 void MeasuringTextTestCase::WindowGetTextExtent()