tools/graph2dot: Check for av_malloc() failure

Fixes CID1271047
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

tools/graph2dot.c

@@ -157,9 +157,17 @@ int main(int argc, char **argv)
         struct line *line, *last_line, *first_line;
         char *p;
         last_line = first_line = av_malloc(sizeof(struct line));
+        if (!last_line) {
+            fprintf(stderr, "Memory allocation failure\n");
+            return 1;
+        }
 
         while (fgets(last_line->data, sizeof(last_line->data), infile)) {
             struct line *new_line = av_malloc(sizeof(struct line));
+            if (!new_line) {
+                fprintf(stderr, "Memory allocation failure\n");
+                return 1;
+            }
             count += strlen(last_line->data);
             last_line->next = new_line;
             last_line       = new_line;
@@ -167,6 +175,10 @@ int main(int argc, char **argv)
         last_line->next = NULL;
 
         graph_string = av_malloc(count + 1);
+        if (!graph_string) {
+            fprintf(stderr, "Memory allocation failure\n");
+            return 1;
+        }
         p = graph_string;
         for (line = first_line; line->next; line = line->next) {
             unsigned int l = strlen(line->data);