pdftohmtl: Initialize rotSkewMat

Fixes uninitialized memory read at bug #100314
diff --git a/utils/HtmlFonts.cc b/utils/HtmlFonts.cc
index a12992e..49376d6 100644
--- a/utils/HtmlFonts.cc
+++ b/utils/HtmlFonts.cc
@@ -156,6 +156,7 @@
     pos = font_num; 
   if (!DefaultFont) DefaultFont=new GooString(fonts[font_num].name);
 
+  rotSkewMat[0] = rotSkewMat[1] = rotSkewMat[2] = rotSkewMat[3] = 0;
 }
  
 HtmlFont::HtmlFont(const HtmlFont& x){