lcd: avoid possible NULL dereference

Do not dereference bmp before the check if it is NULL.

The problem was indicated by cppcheck.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

common/lcd.c

@@ -578,7 +578,7 @@ int lcd_display_bitmap(ulong bmp_image, int x, int y)
 	unsigned long pwidth = panel_info.vl_col;
 	unsigned colors, bpix, bmp_bpix;
 	int hdr_size;
-	struct bmp_color_table_entry *palette = bmp->color_table;
+	struct bmp_color_table_entry *palette;
 
 	if (!bmp || !(bmp->header.signature[0] == 'B' &&
 		bmp->header.signature[1] == 'M')) {
@@ -587,6 +587,7 @@ int lcd_display_bitmap(ulong bmp_image, int x, int y)
 		return 1;
 	}
 
+	palette = bmp->color_table;
 	width = get_unaligned_le32(&bmp->header.width);
 	height = get_unaligned_le32(&bmp->header.height);
 	bmp_bpix = get_unaligned_le16(&bmp->header.bit_count);