Strange error with "Attempted to assign to readonly property" when providing a style to ion-card

hello all,

i recently updated an older project to ionic 3 and since then i get a strange error:
“Attempted to assign to readonly property” in Safari.
It happens basically when I fill an array… here is a simplified version:

<ion-card [style]="supplyStyle()">

where supplyStyle is

    var str="";
    return this.sanitizer.bypassSecurityTrustStyle(str);

This error does not happen in Chrome or Firefox … Only in Safari ( 10.1.2 )
Any Pointers?

why are you write [] to style tag, any special reason ?