perf annotate: Fix hashmap__new() error checking

The hashmap__new() function never returns NULL, it returns error
pointers. Fix the error checking to match.

Additionally, set src->samples to NULL to prevent any later code from
accidentally using the error pointer.

Fixes: d3e7cad ("perf annotate: Add a hashmap for symbol histogram")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tianyou Li <tianyou.li@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: Chen Ni

tools/perf/util/annotate.c

@@ -44,6 +44,7 @@
 #include "strbuf.h"
 #include <regex.h>
 #include <linux/bitops.h>
+#include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/zalloc.h>
@@ -137,8 +138,10 @@ static int annotated_source__alloc_histograms(struct annotated_source *src,
 		return -1;
 
 	src->samples = hashmap__new(sym_hist_hash, sym_hist_equal, NULL);
-	if (src->samples == NULL)
+	if (IS_ERR(src->samples)) {
 		zfree(&src->histograms);
+		src->samples = NULL;
+	}
 
 	return src->histograms ? 0 : -1;
 }