Crash when using t or f vi movements like in ct_

[jolmg]

Description

In vi normal mode, using commands like dfx or ct_ crash IRB.

Example

String is "foo_bar", cursor is on the "f", and the editing mode is vi normal mode. "df_" is then typed.

Expected behavior

"foo_" is deleted and we're left with "bar" and the cursor on the "b".

Actual behavior

IRB crashes with the exception:

irb(main):001:0> Traceback (most recent call last):
	33: from /usr/bin/irb:23:in `<main>'
	32: from /usr/bin/irb:23:in `load'
	31: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/exe/irb:11:in `<top (required)>'
	30: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:400:in `start'
	29: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:471:in `run'
	28: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:471:in `catch'
	27: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:472:in `block in run'
	26: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:537:in `eval_input'
	25: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:150:in `each_top_level_statement'
	24: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:150:in `catch'
	23: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:151:in `block in each_top_level_statement'
	22: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:151:in `loop'
	21: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:154:in `block (2 levels) in each_top_level_statement'
	20: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/ruby-lex.rb:182:in `lex'
	19: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:518:in `block in eval_input'
	18: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:704:in `signal_status'
	17: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb.rb:519:in `block (2 levels) in eval_input'
	16: from /usr/lib/ruby/gems/2.7.0/gems/irb-1.2.7/lib/irb/input-method.rb:294:in `gets'
	15: from /usr/lib/ruby/2.7.0/forwardable.rb:235:in `readmultiline'
	14: from /usr/lib/ruby/2.7.0/forwardable.rb:235:in `readmultiline'
	13: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:175:in `readmultiline'
	12: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:238:in `inner_readline'
	11: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:238:in `loop'
	10: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:239:in `block in inner_readline'
	 9: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:270:in `read_io'
	 8: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:270:in `loop'
	 7: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:311:in `block in read_io'
	 6: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:240:in `block (2 levels) in inner_readline'
	 5: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:240:in `each'
	 4: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline.rb:241:in `block (3 levels) in inner_readline'
	 3: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline/line_editor.rb:834:in `input_key'
	 2: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline/line_editor.rb:792:in `normal_char'
	 1: from /usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline/line_editor.rb:751:in `process_key'
/usr/lib/ruby/gems/2.7.0/gems/reline-0.1.5/lib/reline/line_editor.rb:698:in `block in run_for_operators': undefined method `call' for nil:NilClass (NoMethodError)

Terminal Emulator

urxvt v9.22

ruby 2.7.2p137