Do not write empty lines from above, do not reset hl for empty lines

Fixes #1322

powerline/bindings/zsh/__init__.py

@@ -178,7 +178,8 @@ class Prompt(object):
 				width=zsh.columns() - zle_rprompt_indent,
 				segment_info=segment_info,
 			):
-				r += line + '\n'
+				if line:
+					r += line + '\n'
 		r += self.powerline.render(
 			width=zsh.columns(),
 			side=self.side,

powerline/commands/main.py

@@ -159,7 +159,8 @@ def write_output(args, powerline, segment_info, write):
 			segment_info=segment_info,
 			mode=segment_info.get('mode', None),
 		):
-			write(line + '\n')
+			if line:
+				write(line + '\n')
 		args.side = args.side[len('above'):]
 
 	if args.side:

powerline/renderer.py

@@ -378,7 +378,9 @@ class Renderer(object):
 		elif output_width:
 			current_width = self._render_length(theme, segments, divider_widths)
 
-		rendered_highlighted = ''.join([segment['_rendered_hl'] for segment in self._render_segments(theme, segments)]) + self.hlstyle()
+		rendered_highlighted = ''.join([segment['_rendered_hl'] for segment in self._render_segments(theme, segments)])
+		if rendered_highlighted:
+			rendered_highlighted += self.hlstyle()
 
 		return construct_returned_value(rendered_highlighted, segments, current_width, output_raw, output_width)