Fix crash when expect_corrections runs into an infinite loop

lib/rubocop/rspec/expect_offense.rb

@@ -133,14 +133,14 @@ def expect_offense(source, file = nil, severity: nil, **replacements)
             "#{@processed_source.diagnostics.map(&:render).join("\n")}"
         end
 
-        offenses = _investigate(cop, @processed_source)
+        @offenses = _investigate(cop, @processed_source)
         actual_annotations =
-          expected_annotations.with_offense_annotations(offenses)
+          expected_annotations.with_offense_annotations(@offenses)
 
         expect(actual_annotations).to eq(expected_annotations), ''
-        expect(offenses.map(&:severity).uniq).to eq([severity]) if severity
+        expect(@offenses.map(&:severity).uniq).to eq([severity]) if severity
 
-        offenses
+        @offenses
       end
 
       def expect_correction(correction, loop: true)
@@ -157,7 +157,7 @@ def expect_correction(correction, loop: true)
           break corrected_source if corrected_source == @processed_source.buffer.source
 
           if iteration > RuboCop::Runner::MAX_ITERATIONS
-            raise RuboCop::Runner::InfiniteCorrectionLoop.new(@processed_source.path, [])
+            raise RuboCop::Runner::InfiniteCorrectionLoop.new(@processed_source.path, [@offenses])
           end
 
           # Prepare for next loop

lib/rubocop/runner.rb

@@ -16,7 +16,11 @@ def initialize(path, offenses_by_iteration, loop_start: -1)
         root_cause = offenses_by_iteration[loop_start..-1]
                      .map { |x| x.map(&:cop_name).uniq.join(', ') }
                      .join(' -> ')
-        super "Infinite loop detected in #{path} and caused by #{root_cause}"
+
+        message = 'Infinite loop detected'
+        message += " in #{path}" if path
+        message += " and caused by #{root_cause}" if root_cause
+        super message
       end
     end