lvfntman: fix LVFontGlobalGlyphCache::removeNoLock (#532)

The cache size was not updated when removing the last item.
Potential impact: negligible, between 64 and 316 bytes on each book
opening after the first one, resulting in a ~1% reduction in usable
cache size after opening 17 books.

crengine/src/lvfntman.cpp

@@ -1270,6 +1270,7 @@ void LVFontGlobalGlyphCache::remove( LVFontGlyphCacheItem * item )
 
 void LVFontGlobalGlyphCache::removeNoLock( LVFontGlyphCacheItem * item )
 {
+    size -= item->getSize();
     if ( item==head )
         head = item->next_global;
     if ( item==tail )
@@ -1282,7 +1283,6 @@ void LVFontGlobalGlyphCache::removeNoLock( LVFontGlyphCacheItem * item )
         item->next_global->prev_global = item->prev_global;
     item->next_global = NULL;
     item->prev_global = NULL;
-    size -= item->getSize();
 }
 
 void LVFontGlobalGlyphCache::clear()