Out of memory when using uinteger array (*solved*)

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Code:

' tn = TriangleNumber, mt = MaximumTriangles (# of), rn = RandomNumber, GraphicWidth, GraphicHeight, zn = ZeroNumber (Modifier) 'DIM udg(7) AS UBYTE => {0,1,3,7,15,31,63,127}
INK 6: PAPER 1: FLASH 0: BRIGHT 1: OVER 0: INVERSE 0: DIM tn, mt, rn, gw, gh, znw, znh AS UBYTE: DIM x(4,4) AS UINTEGER: DIM y(4,4) AS UINTEGER
'DIM x(4,4) AS FLOAT: DIM y(4,4) AS FLOAT
tn=0: mt=0: rn=0: znw=0: znh=16
gw=255: gh=175+znh: BORDER 1: CLS: PRINT AT 10,5;"The Sierpinski Triangle";: tn=1: mt=4 '256-1 '176-1
x(tn,1)=znw: y(tn,1)=znh: x(tn,2)=gw/2: y(tn,2)=gh: x(tn,3)=gw: y(tn,3)=znh: GOSUB FirstPoint: tn=tn+1
x(tn,1)=znw: y(tn,1)=gh: x(tn,2)=gw/2: y(tn,2)=znh: x(tn,3)=gw: y(tn,3)=gh: GOSUB FirstPoint: tn=tn+1
x(tn,1)=znw: y(tn,1)=gh: x(tn,2)=gw: y(tn,2)=gh/2: x(tn,3)=znw: y(tn,3)=znh: GOSUB FirstPoint: tn=tn+1
x(tn,1)=gw: y(tn,1)=gh: x(tn,2)=znw: y(tn,2)=gh/2: x(tn,3)=gw: y(tn,3)=znh: GOSUB FirstPoint
tn=1: PRINT AT 12,4;"Press any key to continue";
ScanAnyKey:
IF INKEY$="" THEN GO TO ScanAnyKey: END IF
RANDOMIZE : CLS
DrawTriangles:
rn=INT (RND*3)+1
x(tn,4)=(x(tn,4)+x(tn,rn))/2
y(tn,4)=(y(tn,4)+y(tn,rn))/2
PLOT x(tn,4),y(tn,4)
tn=tn+1: IF tn>mt THEN tn=1: END IF
GO TO DrawTriangles
FirstPoint:
x(tn,4)=x(tn,2): y(tn,4)=y(tn,2): RETURN

This crashes after a few pixels drawn with an out of memory error while if you use float it works fine under
the latest version of the compiler. In version 1.2.6 uinteger works without a hitch. The compilation options are:
zxb Triangles.bas --optimize=2 --output=TRIANGLES.ASM --asm --org=24576 --array-base=1 --string-base=1 --heap-size=1024
zxbasm TRIANGLES.ASM --output=TRIANGLES --tap --BASIC --autorun

On to another subject, what is the correct syntax for "DIM udg(7) AS UBYTE => {0,1,3,7,15,31,63,127}"
as a multidimensional array? I tried "DIM ma(2,2) AS UBYTE => {1,4,6,2,0,55}" but it did not work.