Implement changes to ThemeHelper requested by review

- turned theme_attribute_map into frozen constant ATTRIBUTE_MAP
- early return if no theme exists, instead of if-block
- usage of Hash#key? instead Hash[k] to confirm existence of key in hash
- Early skip/next if key is not present in Hash instead of if-block

app/helpers/theme_helper.rb

@@ -1,49 +1,49 @@
 module ThemeHelper
-  def render_theme
-    theme_attribute_map = {
-      'primary_color' => 'primary',
-      'primary_text' => 'primary-text',
-      'danger_color' => 'danger',
-      'danger_text' => 'danger-text',
-      'warning_color' => 'warning',
-      'warning_text' => 'warning-text',
-      'info_color' => 'info',
-      'info_text' => 'info-text',
-      'success_color' => 'success',
-      'success_text' => 'success-text',
-      'dark_color' => 'dark',
-      'dark_text' => 'dark-text',
-      'light_color' => 'light',
-      'light_text' => 'light-text',
-      'raised_background' => 'raised-bg',
-      'raised_accent' => 'raised-accent',
-      'background_color' => 'background',
-      'body_text' => 'body-text',
-      'input_color' => 'input-bg',
-      'input_text' => 'input-text',
-      'muted_text' => 'muted-text'
-    }
+  ATTRIBUTE_MAP = {
+    'primary_color' => 'primary',
+    'primary_text' => 'primary-text',
+    'danger_color' => 'danger',
+    'danger_text' => 'danger-text',
+    'warning_color' => 'warning',
+    'warning_text' => 'warning-text',
+    'info_color' => 'info',
+    'info_text' => 'info-text',
+    'success_color' => 'success',
+    'success_text' => 'success-text',
+    'dark_color' => 'dark',
+    'dark_text' => 'dark-text',
+    'light_color' => 'light',
+    'light_text' => 'light-text',
+    'raised_background' => 'raised-bg',
+    'raised_accent' => 'raised-accent',
+    'background_color' => 'background',
+    'body_text' => 'body-text',
+    'input_color' => 'input-bg',
+    'input_text' => 'input-text',
+    'muted_text' => 'muted-text'
+  }.freeze
 
+  def render_theme
     theme = get_active_theme
 
-    if theme
+    return unless theme
 
     body = ":root {\n"
-      theme.attributes.each do |k, v|
-        if theme_attribute_map[k]
-          if k.include? "text"
-            hex = get_hex_color_from_theme_value(v)
-            body += "\t--#{theme_attribute_map[k]}: #{get_decimal_triplet_from_hex(hex)};\n"
-          else
-            body += "\t--#{theme_attribute_map[k]}: ##{get_hex_color_from_theme_value(v)};\n"
-          end
-        end
+
+    theme.attributes.each do |k, v|
+      next unless ATTRIBUTE_MAP.key?(k)
+
+      if k.include? "text"
+        hex = get_hex_color_from_theme_value(v)
+        body += "\t--#{ATTRIBUTE_MAP[k]}: #{get_decimal_triplet_from_hex(hex)};\n"
+      else
+        body += "\t--#{ATTRIBUTE_MAP[k]}: ##{get_hex_color_from_theme_value(v)};\n"
       end
-
-      body += "}"
-
-      content_tag(:style, body)
     end
+
+    body += "}"
+
+    content_tag(:style, body)
   end
 
   def get_active_theme