font-patcher: Fix crash if no roman characters

[why]
When we can not detect the cell width, for example because there are no
glyphs in the range of extrended-roman that we examine, the width will
be zero and that will result in a crash later on (on rescaling).

[how]
Just abort if height or width are zero or negative.

Related: #1460

Signed-off-by: Fini Jastrow <[email protected]>

font-patcher

@@ -6,7 +6,7 @@
 from __future__ import absolute_import, print_function, unicode_literals
 
 # Change the script version when you edit this script:
-script_version = "4.8.2"
+script_version = "4.8.3"
 
 version = "3.1.1"
 projectName = "Nerd Fonts"
@@ -1212,7 +1212,7 @@ class font_patcher:
                 'height': self.sourceFont.descent + self.sourceFont.ascent,
             }
             our_btb = self.sourceFont.descent + self.sourceFont.ascent
-        elif self.font_dim['height'] < 0:
+        if self.font_dim['height'] <= 0:
             logger.critical("Can not detect sane font height")
             sys.exit(1)
 
@@ -1266,6 +1266,9 @@ class font_patcher:
         if self.font_dim['width'] < self.font_dim['xmax']:
             logger.debug("Font has negative right side bearing in extended glyphs")
             self.font_dim['xmax'] = self.font_dim['width'] # In fact 'xmax' is never used
+        if self.font_dim['width'] <= 0:
+            logger.critical("Can not detect sane font width")
+            sys.exit(1)
         logger.debug("Final font cell dimensions %d w x %d h", self.font_dim['width'], self.font_dim['height'])
 
         self.xavgwidth.append(self.args.xavgwidth)