summary: Fix empty list case

Fixes: #6557.

mesonbuild/interpreter.py

@@ -1783,6 +1783,8 @@ class Summary:
                     formatted_values.append(mlog.green('YES') if i else mlog.red('NO'))
                 else:
                     formatted_values.append(i)
+            if not formatted_values:
+                formatted_values = ['']
             self.sections[section][k] = formatted_values
             self.max_key_len = max(self.max_key_len, len(k))
 

run_unittests.py

@@ -4254,6 +4254,7 @@ recommended as it is not supported on some platforms''')
                          A list: string
                                  1
                                  True
+                     empty list: 
                        A number: 1
                             yes: YES
                              no: NO

test cases/unit/72 summary/meson.build

@@ -7,6 +7,7 @@ summary({'Some boolean': false,
          'Another boolean': true,
          'Some string': 'Hello World',
          'A list': ['string', 1, true],
+         'empty list': [],
         }, section: 'Configuration')
 summary('A number', 1, section: 'Configuration')
 summary('yes', true, bool_yn : true, section: 'Configuration')