Explicitly define html_escape

In async actions the view context doesn't seem to be available,
from where html_escape was called before.

So we explicitly call out to it now.

Also improved some error reporting, that before was just swalloing
errors without a proper stacktrace or real error.

Author: PragTob

app/concepts/matestack/ui/core/page/page.rb

@@ -94,7 +94,7 @@ def show(component_key=nil, only_page=false)
         begin
           render_child_component component_key
         rescue => e
-          raise "Component '#{component_key}' could not be resolved."
+          raise "Component '#{component_key}' could not be resolved, because of #{e},\n#{e.backtrace.join("\n")}"
         end
       end
     end

lib/matestack/ui/core/cell.rb

@@ -22,9 +22,9 @@ def template_options_for(_options)
           }
         end
 
-        # def html_escape(string)
-
-        # end
+        def html_escape(string)
+          ERB::Util.html_escape(string)
+        end
       end
     end
   end

spec/usage/base/component_spec.rb

@@ -345,7 +345,6 @@ def response
       after_content = element.text
 
       expect(before_content).not_to eq(after_content)
-
     end
 
     it "components can render dynamic content with vue.js involved if inherit from 'Matestack::Ui::DynamicComponent'" do