evas - map render - quick fix for segv in new map renderer

u or v go below 0... sometimes. right now i don't know the full path
to there, bute crashes with flat theme when the busy spinner shows
over an ibar icon when you launch... this at least stops that.

this needs hunting in more detail than i'm going to do on my laptop
on the couch...

src/lib/evas/common/evas_map_image_internal_high.c

@@ -396,6 +396,9 @@ _map_triangle_draw_linear(RGBA_Image *src, RGBA_Image *dst,
         dx = 1 - (_xa - x1);
         u = _ua + dx * _dudx;
         v = _va + dx * _dvdx;
+        // FIXME: sometimes u and v are < 0 - don'tc crash
+        if (u < 0) u = 0;
+        if (v < 0) v = 0;
 
         if (col_blend)
           {