Avoid warning for pm_token_buffer_t initialization

* This was causing this error on macOS Mojave:
  src/prism.c:8216:48: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
            pm_token_buffer_t token_buffer = { 0 };
                                               ^

Author: eregon

src/prism.c

@@ -8247,7 +8247,7 @@ parser_lex(pm_parser_t *parser) {
 
             // If we haven't found an escape yet, then this buffer will be
             // unallocated since we can refer directly to the source string.
-            pm_token_buffer_t token_buffer = { 0 };
+            pm_token_buffer_t token_buffer = { { 0 }, 0 };
 
             while (breakpoint != NULL) {
                 // If we hit a null byte, skip directly past it.
@@ -8423,7 +8423,7 @@ parser_lex(pm_parser_t *parser) {
             // characters.
             const uint8_t *breakpoints = lex_mode->as.regexp.breakpoints;
             const uint8_t *breakpoint = pm_strpbrk(parser, parser->current.end, breakpoints, parser->end - parser->current.end);
-            pm_token_buffer_t token_buffer = { 0 };
+            pm_token_buffer_t token_buffer = { { 0 }, 0 };
 
             while (breakpoint != NULL) {
                 // If we hit a null byte, skip directly past it.
@@ -8612,7 +8612,7 @@ parser_lex(pm_parser_t *parser) {
 
             // If we haven't found an escape yet, then this buffer will be
             // unallocated since we can refer directly to the source string.
-            pm_token_buffer_t token_buffer = { 0 };
+            pm_token_buffer_t token_buffer = { { 0 }, 0 };
 
             while (breakpoint != NULL) {
                 // If we hit the incrementor, then we'll increment then nesting and
@@ -8873,7 +8873,7 @@ parser_lex(pm_parser_t *parser) {
             }
 
             const uint8_t *breakpoint = pm_strpbrk(parser, parser->current.end, breakpoints, parser->end - parser->current.end);
-            pm_token_buffer_t token_buffer = { 0 };
+            pm_token_buffer_t token_buffer = { { 0 }, 0 };
             bool was_escaped_newline = false;
 
             while (breakpoint != NULL) {