lavfi/pad: avoid buffer overflow in buffer_needs_copy()

Replace & with short-circuit &&.
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

libavfilter/vf_pad.c

@@ -300,7 +300,7 @@ static int buffer_needs_copy(PadContext *s, AVFrame *frame, AVBufferRef *buf)
             return 1;
 
 #define SIGN(x) ((x) > 0 ? 1 : -1)
-        for (j = 0; j < FF_ARRAY_ELEMS(planes) & planes[j] >= 0; j++) {
+        for (j = 0; j < FF_ARRAY_ELEMS(planes) && planes[j] >= 0; j++) {
             int hsub1 = s->draw.hsub[planes[j]];
             uint8_t *start1 = frame->data[planes[j]];
             uint8_t *end1   = start1 + (frame->height >> hsub1) *