Use zero-initialization for character arrays

It makes some not-fully-compliant compilers happy

apps/calculation/calculation.cpp

@@ -6,8 +6,8 @@ using namespace Poincare;
 namespace Calculation {
 
 Calculation::Calculation() :
-  m_inputText(""),
-  m_outputText(""),
+  m_inputText(),
+  m_outputText(),
   m_input(nullptr),
   m_inputLayout(nullptr),
   m_output(nullptr),

apps/code/program.cpp

@@ -3,7 +3,7 @@
 namespace Code {
 
 Program::Program() :
-  m_buffer("")
+  m_buffer()
 {
   const char program[] = R"(# This program draws a Mandelbrot fractal set
 # N_iteration: degree of precision

apps/sequence/sequence.cpp

@@ -13,8 +13,8 @@ namespace Sequence {
 Sequence::Sequence(const char * text, KDColor color) :
   Function(text, color),
   m_type(Type::Explicite),
-  m_firstInitialConditionText(""),
-  m_secondInitialConditionText(""),
+  m_firstInitialConditionText(),
+  m_secondInitialConditionText(),
   m_firstInitialConditionExpression(nullptr),
   m_secondInitialConditionExpression(nullptr),
   m_firstInitialConditionLayout(nullptr),

escher/src/buffer_text_view.cpp

@@ -5,7 +5,7 @@
 BufferTextView::BufferTextView(KDText::FontSize size, float horizontalAlignment, float verticalAlignment,
     KDColor textColor, KDColor backgroundColor) :
   TextView(size, horizontalAlignment, verticalAlignment, textColor, backgroundColor),
-  m_buffer("")
+  m_buffer()
 {
 }