Make sure ThemeConfig is non-null when loading resources

When the device boots into safemode, the theme config will end up
being null and we need to check that prior to using it to retrieve
resources for the StatusBarIconView

This fixes CYAN-5009

Change-Id: I1a90bc9f9c65cb41a6e58947bbd1b6d7728a952b
Themes: Add ability to apply color filters to composed icons

Themes can include one or more of the following filter tags in
assets/icons/res/xml/appfilter.xml

    <!-- HUE filter
         Integer value between -180 and 180 representing the degree.
         0 = no change
    -->
    <filter name="hue">0</filter>

    <!-- SATURATION filter.
         0 = grayscale, 100 = no change, 200 = over saturated
    -->
    <filter name="saturation">0</filter>

    <!-- BRIGHTNESS filter.
         0 = pitch black, 100 = no change, 200 = 200% brightness
    -->
    <filter name="brightness">100</filter>

    <!-- CONTRAST filter.
         -100 = minimal contrast, 0 = no change, 100 = maximum contrast
    -->
    <filter name="contrast">100</filter>

    <!-- ALPHA filter.
         0 = transparent, 100 = opaque
    -->
    <filter name="alpha">75</filter>

    <!-- INVERT filter.
         Valid values are true or false
         true = invert colors
    -->
    <filter name="invert">false</filter>

    <!-- TINT filter.
         A hexadecimal value representing ARGB
    -->
    <filter name="tint">#ff0000ff</filter>

Change-Id: I2431237dd2766176be16c730020557ce87d623e4