fdo#73280 - always advance the iterator to avoid an infinite loop.

Change-Id: I62f2d8ec5d6d62f1dbe9657cfbbbc90c56cce812

vcl/generic/glyphs/glyphcache.cxx

@@ -374,6 +374,8 @@ void ServerFont::GarbageCollect( long nMinLruIndex )
             GlyphCache::GetInstance().RemovingGlyph( rGD );
             it = maGlyphList.erase( it );
         }
+        else
+            ++it;
     }
 }