Fix full dps visual bug on gem dropdown

[Paliak]

Description of the problem being solved:

When hovering over a gem in the gem selection dropdown while having anything other than full dps selected in the sort gems by dropdown the tooltip would show that the player loses all full dps (see screen shots). This was caused by a funky lua behaviour here:

PathOfBuilding/src/Modules/Build.lua

Lines 1864 to 1866 in c76a5fe

	if statData.stat == "FullDPS" and not GlobalCache.useFullDPS and not self.viewMode == "TREE" then
	diff = 0
	end

The above condition would return false even though self.viewMode was not "TREE" see below minimal repro:

test1 = "test1"
test2 = false
test3 = "justtest"

print(test1 == "test1" and not test2 and not test3 == "test3") -- false -- the condition currently
print((test1 == "test1" and not test2 and not test3) == "test3") -- false
print(test1 == "test1" and not test2 and not (test3 == "test3")) -- true
print(test1 == "test1" and not test2 and test3 ~= "test3") -- true -- the condition this pr changes it to

Before screenshot:

After screenshot: