UPBGE: Fix shader recompilation after error.

Previously when a filter failed its compilation, it was
impossible to recompile new sources.
This was caused by the fact that in RAS_Shader::LinkProgram
the variable m_error was first checked and if it was true
when we discard shader compilation. But this variable was
set when the shader failed for the first time. At the end
the shader always discarded the next compilation.

To fix this issue the compilation discard is removed.

In the same time the 0 and 1 are replaced by true or false for
boolean variable.

Bug reported by TwisterGE.

source/gameengine/Ketsji/BL_Shader.cpp

@@ -273,7 +273,7 @@ KX_PYMETHODDEF_DOC(BL_Shader, setSource, " setSource(vertexProgram, fragmentProg
 
 		m_progs[VERTEX_PROGRAM] = "";
 		m_progs[FRAGMENT_PROGRAM] = "";
-		m_use = 0;
+		m_use = false;
 		Py_RETURN_NONE;
 	}
 	return nullptr;
@@ -320,7 +320,7 @@ KX_PYMETHODDEF_DOC(BL_Shader, setSourceList, " setSourceList(sources, apply)")
 		for (unsigned short i = 0; i < MAX_PROGRAM; ++i) {
 			m_progs[i] = "";
 		}
-		m_use = 0;
+		m_use = false;
 		return nullptr;
 	}
 

source/gameengine/Ketsji/KX_BlenderMaterial.cpp

@@ -868,12 +868,10 @@ KX_PYMETHODDEF_DOC(KX_BlenderMaterial, getShader, "getShader()")
 
 	if (!m_shader) {
 		m_shader = new BL_Shader();
-		if (!m_shader->GetError()) {
-			// Set the material to use custom shader.
-			m_flag &= ~RAS_BLENDERGLSL;
-			m_shader->InitTexCo(m_textures);
-			m_scene->GetBucketManager()->UpdateShaders(this);
-		}
+		// Set the material to use custom shader.
+		m_flag &= ~RAS_BLENDERGLSL;
+		m_shader->InitTexCo(m_textures);
+		m_scene->GetBucketManager()->UpdateShaders(this);
 	}
 
 	if (!m_shader->GetError()) {

source/gameengine/Rasterizer/RAS_Shader.cpp

@@ -160,8 +160,8 @@ bool RAS_Shader::Ok() const
 
 RAS_Shader::RAS_Shader()
 	:m_shader(nullptr),
-	m_use(0),
-	m_error(0),
+	m_use(false),
+	m_error(false),
 	m_dirty(true)
 {
 	for (unsigned short i = 0; i < MAX_PROGRAM; ++i) {
@@ -300,10 +300,6 @@ bool RAS_Shader::LinkProgram()
 	std::string frag;
 	std::string geom;
 
-	if (m_error) {
-		goto program_error;
-	}
-
 	if (m_progs[VERTEX_PROGRAM].empty() || m_progs[FRAGMENT_PROGRAM].empty()) {
 		CM_Error("invalid GLSL sources.");
 		return false;
@@ -315,18 +311,12 @@ bool RAS_Shader::LinkProgram()
 	m_shader = GPU_shader_create(vert.c_str(), frag.c_str(), geom.empty() ? nullptr : geom.c_str(),
 									nullptr, nullptr, 0, 0, 0);
 	if (!m_shader) {
-		goto program_error;
+		m_error = true;
+		return false;
 	}
 
-	m_error = 0;
+	m_error = false;
 	return true;
-
-	program_error:
-	{
-		m_use = 0;
-		m_error = 1;
-		return false;
-	}
 }
 
 void RAS_Shader::ValidateProgram()