formatting: fix exception when formatting the integer 0 using "%e"

basis/formatting/formatting-tests.factor

@@ -36,6 +36,7 @@ IN: formatting.tests
 { "1.4" } [ 135/100 "%.1f" sprintf ] unit-test
 { "4" } [ 7/2 "%.0f" sprintf ] unit-test
 { "1" } [ 1.0 "%.0f" sprintf ] unit-test
+{ "0.0e+00" } [ 0 "%.1e" sprintf ] unit-test
 { "  1.23" } [ 1.23456789 "%6.2f" sprintf ] unit-test
 { "001100" } [ 12 "%06b" sprintf ] unit-test
 { "==14" } [ 12 "%'=4o" sprintf ] unit-test

basis/formatting/formatting.factor

@@ -61,7 +61,7 @@ IN: formatting
 : format-fast-scientific? ( x digits -- x' digits ? )
     over float? [ t ]
     [ 2dup
-        [ abs integer-log10 abs 308 < ]
+        [ [ t ] [ abs integer-log10 abs 308 < ] if-zero ]
         [ 15 < ] bi* and
         [ [ [ >float ] dip ] when ] keep
     ] if ;