Update VRAM pointer when copying row of zeros to map

src/map.s

@@ -113,9 +113,8 @@ Map_Load::
 ; @param c Map Y coordinate (signed)
 ; @param hl Start of the row to write
 write_map_row:
-    push bc ; sp + 7
-    push de ; sp + 5
-    push hl ; sp + 3
+    push bc
+    push de
 
     ; If Y < 0, write a row of 0s
     bit 7, c
@@ -135,12 +134,13 @@ write_map_row:
     dec d
     jr nz, .zero_row_loop
 .zero_row_done:
-    pop hl
     pop de
     pop bc
     ret
 
 .begin_writing:
+    push hl
+
     ; Allocate 2 bytes for map pointer
     ; Allocate 1 byte for number of tiles left
     add sp, -3