Revert "Fixed issue of canvas size limitations"

This reverts commit 87c05de6e7.

js/Startup.js

@@ -18,12 +18,6 @@ const Startup = (() => {
         var height = Util.getValue('size-height' + splashPostfix);
         var selectedPalette = Util.getText('palette-button' + splashPostfix);
     
-        //Checks whether width and height values are not invalid
-        if(width <= 0 || height <= 0) {
-            alert("Please enter valid width and height");
-            return;
-        }
-        
         newPixel(FileManager.defaultLPE(width,height));
         resetInput();