Don’t save font if it has no name

Closes #661, #603.

lib/mixins/fonts.coffee

@@ -1,25 +1,25 @@
 PDFFont = require '../font'
 
-module.exports = 
+module.exports =
   initFonts: ->
     # Lookup table for embedded fonts
     @_fontFamilies = {}
     @_fontCount = 0
-    
+
     # Font state
     @_fontSize = 12
     @_font = null
-    
+
     @_registeredFonts = {}
-    
+
     # Set the default font
     @font 'Helvetica'
-    
+
   font: (src, family, size) ->
     if typeof family is 'number'
       size = family
       family = null
-    
+
     # check registered fonts if src is a string
     if typeof src is 'string' and @_registeredFonts[src]
       cacheKey = src
@@ -27,40 +27,42 @@ module.exports =
     else
       cacheKey = family or src
       cacheKey = null unless typeof cacheKey is 'string'
-    
-    @fontSize size if size?  
-    
+
+    @fontSize size if size?
+
     # fast path: check if the font is already in the PDF
     if font = @_fontFamilies[cacheKey]
       @_font = font
       return this
-      
+
     # load the font
     id = 'F' + (++@_fontCount)
     @_font = PDFFont.open(this, src, family, id)
-    
+
     # check for existing font familes with the same name already in the PDF
     # useful if the font was passed as a buffer
     if font = @_fontFamilies[@_font.name]
       @_font = font
       return this
-      
+
     # save the font for reuse later
     if cacheKey
       @_fontFamilies[cacheKey] = @_font
-      
-    @_fontFamilies[@_font.name] = @_font
+
+    if @_font.name
+      @_fontFamilies[@_font.name] = @_font
+
     return this
-    
+
   fontSize: (@_fontSize) ->
     return this
-    
+
   currentLineHeight: (includeGap = false) ->
     @_font.lineHeight @_fontSize, includeGap
-    
+
   registerFont: (name, src, family) ->
-    @_registeredFonts[name] = 
+    @_registeredFonts[name] =
       src: src
       family: family
-      
+
     return this