[ruby/prism] fix: float suffix at end of file

Found by fuzzing.

https://github.com/ruby/prism/commit/d77d4fe2b7

prism/prism.c

@@ -6338,7 +6338,7 @@ lex_optional_float_suffix(pm_parser_t *parser, bool* seen_e) {
         (void) (match(parser, '+') || match(parser, '-'));
         *seen_e = true;
 
-        if (pm_char_is_decimal_digit(*parser->current.end)) {
+        if (pm_char_is_decimal_digit(peek(parser))) {
             parser->current.end++;
             parser->current.end += pm_strspn_decimal_number_validate(parser, parser->current.end);
             type = PM_TOKEN_FLOAT;

test/prism/fuzzer_test.rb

@@ -35,6 +35,7 @@ module Prism
     snippet "escaped unicode at end of file 7", '"\\u3'
     snippet "escaped unicode at end of file 8", '"\\u33'
     snippet "escaped unicode at end of file 9", '"\\u333'
+    snippet "float suffix at end of file", "1e"
 
     snippet "statements node with multiple heredocs", <<~EOF
       for <<A + <<B