Check the result of fgets() to deal with warn_unused_result

Some C library versions have __attribute__((warn_unused_result)) on
fgets(). We really don't care since we are just throwing the data
away, but check the result anyways.

src/shell-recorder.c

@@ -221,7 +221,8 @@ get_memory_target (void)
           return mem_total / 2;
         }
       /* Skip to the next line and discard what we read */
-      fgets(line_buffer, sizeof(line_buffer), f);
+      if (fgets(line_buffer, sizeof(line_buffer), f) == NULL)
+        break;
     }
 
   fclose(f);