physical: Fix readability-implicit-bool-conversion
```
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../physical.cpp:135:10: error: implicit conversion 'std::basic_string<char>::size_type' (aka 'unsigned long') -> bool [readability-implicit-bool-conversion,-warnings-as-errors]
if (!color.length())
~^
== 0u
```
Change-Id: I0bb5e13bec6fbe8b21a89af695ca8f9535e3cdab
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/physical.cpp b/physical.cpp
index fc518f8..aa9d3e4 100644
--- a/physical.cpp
+++ b/physical.cpp
@@ -128,7 +128,7 @@
{
static const std::string prefix =
"xyz.openbmc_project.Led.Physical.Palette.";
- if (!color.length())
+ if (color.empty())
return;
std::string tmp = color;
tmp[0] = toupper(tmp[0]);