Compiler: fix crash when formatting syntax error inside macro (#8055)

spec/compiler/semantic/macro_spec.cr

@@ -1427,4 +1427,12 @@ describe "Semantic: macro" do
       ),
       "can't instantiate abstract class Foo"
   end
+
+  it "doesn't crash on syntax error inside macro (regression, #8038)" do
+    expect_raises(Crystal::SyntaxException, "unterminated array literal") do
+      semantic(%(
+        {% begin %}[{% end %}
+        ))
+    end
+  end
 end

src/compiler/crystal/exception.cr

@@ -242,22 +242,27 @@ module Crystal
 
     def minimize_indentation(source)
       min_leading_white_space =
-        source.map do |line|
-          if match = line.match(/^(\s+)\S/)
-            spaces = match[1]?
-            spaces.size if spaces
-          end
-        end
-          .compact
-          .min
+        source.min_of? { |line| leading_white_space(line) } || 0
 
-      source = source.map do |line|
-        replace_leading_tabs_with_spaces(line).lchop(" " * min_leading_white_space)
+      if min_leading_white_space > 0
+        source = source.map do |line|
+          replace_leading_tabs_with_spaces(line).lchop(" " * min_leading_white_space)
+        end
       end
 
       {source, min_leading_white_space}
     end
 
+    private def leading_white_space(line)
+      match = line.match(/^(\s+)\S/)
+      return 0 unless match
+
+      spaces = match[1]?
+      return 0 unless spaces
+
+      spaces.size
+    end
+
     def append_expanded_macro(io, source)
       line_number = @line_number
       if @error_trace || !line_number