Suggested change for Tri.be Image Widget plugin, image-widget/image-widget.php, See line 32 and 84 for changes.

image-widget.php

<?php

class Tribe_Image_Widget extends WP_Widget {

	// ...

	private function get_image_html( $instance, $include_link = true ) {

		// Backwards compatible image display.
		if ( $instance['attachment_id'] == 0 && $instance['image'] > 0 ) {
			$instance['attachment_id'] = $instance['image'];
		}

		$output = '';

		if ( $include_link && !empty( $instance['link'] ) ) {
			$attr = array(
				'href' => $instance['link'],
				'target' => $instance['linktarget'],
				'class' => 	$this->widget_options['classname'].'-image-link',
				'title' => ( !empty( $instance['alt'] ) ) ? $instance['alt'] : $instance['title'],
			);
			$attr = apply_filters('image_widget_link_attributes', $attr, $instance );
			$attr = array_map( 'esc_attr', $attr );
			$output = '<a';
			foreach ( $attr as $name => $value ) {
				$output .= sprintf( ' %s="%s"', $name, $value );
			}
			$output .= '>';
		}
		
		$output = apply_filters( 'image_widget_before_image', $output, $instance );

		$size = $this->get_image_size( $instance );
		if ( is_array( $size ) ) {
			$instance['width'] = $size[0];
			$instance['height'] = $size[1];
		} elseif ( !empty( $instance['attachment_id'] ) ) {
			//$instance['width'] = $instance['height'] = 0;
			$image_details = wp_get_attachment_image_src( $instance['attachment_id'], $size );
			if ($image_details) {
				$instance['imageurl'] = $image_details[0];
				$instance['width'] = $image_details[1];
				$instance['height'] = $image_details[2];
			}
		}
		$instance['width'] = abs( $instance['width'] );
		$instance['height'] = abs( $instance['height'] );

		$attr = array();
		$attr['alt'] = $instance['title'];
		if (is_array($size)) {
			$attr['class'] = 'attachment-'.join('x',$size);
		} else {
			$attr['class'] = 'attachment-'.$size;
		}
		$attr['style'] = '';
		if (!empty($instance['maxwidth'])) {
			$attr['style'] .= "max-width: {$instance['maxwidth']};";
		}
		if (!empty($instance['maxheight'])) {
			$attr['style'] .= "max-height: {$instance['maxheight']};";
		}
		if (!empty($instance['align']) && $instance['align'] != 'none') {
			$attr['class'] .= " align{$instance['align']}";
		}
		$attr = apply_filters( 'image_widget_image_attributes', $attr, $instance );

		// If there is an imageurl, use it to render the image. Eventually we should kill this and simply rely on attachment_ids.
		if ( !empty( $instance['imageurl'] ) ) {
			// If all we have is an image src url we can still render an image.
			$attr['src'] = $instance['imageurl'];
			$attr = array_map( 'esc_attr', $attr );
			$hwstring = image_hwstring( $instance['width'], $instance['height'] );
			$output .= rtrim("<img $hwstring");
			foreach ( $attr as $name => $value ) {
				$output .= sprintf( ' %s="%s"', $name, $value );
			}
			$output .= ' />';
		} elseif( abs( $instance['attachment_id'] ) > 0 ) {
			$output .= wp_get_attachment_image($instance['attachment_id'], $size, false, $attr);
		}
		
		$output = apply_filters( 'image_widget_after_image', $output, $instance );

		if ( $include_link && !empty( $instance['link'] ) ) {
			$output .= '</a>';
		}

		return $output;
	}

	// ...

}