fix(colorfilter): support null value

Author: farfromrefug

src/image-colorfilter/index.android.ts

@@ -5,6 +5,10 @@ class ImgExtended {
     nativeImageViewProtected: com.nativescript.image.DraweeView;
     @cssProperty colorMatrix: number[];
     [colorMatrixProperty.setNative](value: number[]) {
+        if (!value) {
+            this.nativeImageViewProtected.setColorFilter(null);
+            return;
+        }
         const arr = Array.create('float', value.length);
         for (let index = 0; index < value.length; index++) {
             arr[index] = value[index];

src/image-colorfilter/index.ios.ts

@@ -44,7 +44,7 @@ class ImgExtended3 {
     _filter: CIFilter;
 
     filteredImage(image: UIImage, filter: CIFilter) {
-        if (image !== null) {
+        if (image !== null && filter !== null) {
             const tmp = CIImage.alloc().initWithImage(image);
             this._filter.setValueForKey(tmp, 'inputImage');
 
@@ -55,7 +55,7 @@ class ImgExtended3 {
             // CGImageRelease(cgim);
             return filteredImage;
         }
-        return null;
+        return image;
     }
     _applyColorFilter(image) {
         if (image) {