[ruby/prism] Fix lexing of foo! when it's a first thing to parse

ruby/prism@7597aca76a

lib/prism/translation/parser/lexer.rb

@@ -289,7 +289,7 @@ def to_a
                 index += 1
               end
             when :tFID
-              if tokens[-1][0] == :kDEF
+              if !tokens.empty? && tokens[-1][0] == :kDEF
                 type = :tIDENTIFIER
               end
             end

test/prism/fixtures/single_method_call_with_bang.txt

@@ -0,0 +1 @@
+foo!

test/prism/snapshots/single_method_call_with_bang.txt

@@ -0,0 +1,15 @@
+@ ProgramNode (location: (1,0)-(1,4))
+├── locals: []
+└── statements:
+    @ StatementsNode (location: (1,0)-(1,4))
+    └── body: (length: 1)
+        └── @ CallNode (location: (1,0)-(1,4))
+            ├── flags: ignore_visibility
+            ├── receiver: ∅
+            ├── call_operator_loc: ∅
+            ├── name: :foo!
+            ├── message_loc: (1,0)-(1,4) = "foo!"
+            ├── opening_loc: ∅
+            ├── arguments: ∅
+            ├── closing_loc: ∅
+            └── block: ∅